Systems and methods for detecting neurological conditions

ABSTRACT

According to various embodiments, there is provided a device including a processor configured to control a robotic system to autonomously position a transducer at a plurality of locations adjacent a subject&#39;s skull and to autonomously locate a window on the subject&#39;s skull within which an artery can be located, from which artery a signal can be returned to the transducer, the signal having an energy level exceeding a predefined threshold.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present disclosure is a continuation of U.S. patent application Ser.No. 15/399,735, titled SYSTEMS AND METHODS FOR DETECTING NEUROLOGICALCONDITIONS, and filed on Jan. 5, 2017, which is incorporated herein byreference in its entirety. The present disclosure claims priority to,and the benefit of, U.S. provisional patent application Ser. No.62/275,192, titled SYSTEMS AND METHODS FOR DETECTING NEUROLOGICALCONDITIONS, and filed on Jan. 5, 2016, which is incorporated herein byreference in its entirety. The present disclosure claims priority to,and the benefit of, U.S. provisional patent application Ser. No.62/338,065, titled REMOTE CENTER OF COMPLIANCE PROBE DEVICE, and filedon May 18, 2016, which is incorporated herein by reference in itsentirety. The present disclosure claims priority to, and the benefit of,U.S. provisional patent application Ser. No. 62/347,527, titled PROBESUPPORT STRUCTURE WITH VARIABLE STIFFNESS, and filed on Jun. 8, 2016,which is incorporated herein by reference in its entirety.

FIELD

Subject matter described herein relates generally to medical devices,and more particularly to a headset including a transducer for diagnosingmedical conditions.

BACKGROUND

Traumatic brain injuries (TBI) affect millions of patients each yearworldwide. Cerebral hemodynamic dysfunction is common following TBI,potentially resulting in catastrophic neurologic sequelae, includinglong-term disability and even death. Current diagnosis and managementmethods are limited to hospital settings (transcranial Dopplerultrasonography—TCD, CT, MRI, etc.). Accordingly, there is a need fordeveloping a medical device that can provide clinical utility ofhospital-based assessment methods outside of a hospital for rapid andreliable assessment using disruptive innovations in TCD ultrasonography.

Various sensory modalities are currently used in major hospitals for theassessment of cerebral hemodynamics within the Circle of Willis arteriesof the brain, including TCD ultrasound, transcranial color-codedsonography (TCCS), phased arrays, and functional Near-InfraredSpectroscopy (fNIRS). These modalities emit energy capable ofpenetrating windows in the skull. Acquiring the cerebral blood flowvelocity (CBFV) signals using such sensory modalities, however, requiresthe placement of a transducer within a specific region of the skull thinenough for the ultrasound waves to penetrate. For example, it is knownthat a thin skull region often exists superior to the patient'szygomatic arch (transtemporal). Other windows often exist at thesuboccipital, transorbital, submandibular portions of the skull. Thelocation of these narrow windows, however, varies significantly fromperson to person based on facial features, and even race or gender. Thisvariation makes insonating—exposing to ultrasound the desired bloodvessel difficult. This difficulty has often restricted TCD use, andother modalities, to major hospitals who engage expert sonographers tooperate the device.

TCD specifically has been widely used clinically since the 1980s tomeasure CBFV within the major conducting arteries and veins of the brain(Circle of Willis). It is currently used in the diagnosis and monitoringa number of neurologic conditions, including the assessment of arteriesafter a subarachnoid haemorrhage (SAH) for vasospasm, aidingpreventative care in children with sickle cell anemia, and riskassessment in embolic stroke patients. TCD utilizes the Doppler effectby emitting ultrasound frequencies typically between 1.6 MHz and 4 MHzand measuring the shift in frequency upon reflection from non-stationarytissue (red blood cells), which are converted to velocity. Depthinformation within the biologic tissue is controlled by time delaysbetween emitting and receiving of the ultrasound waves.

Fully automating TCD use would not only remove the need for an experttechnician but also open the technology up to a broader range ofclinical indications. As such, there is a need for developing aportable, fully automated system to determine appropriate windowlocations.

Existing semi-automated diagnosis methods typically use two degree offreedom robotic mechanisms that can only reorient the TCD probe with panand tilt rotations, emitting energy into the skull and then analyzingthe return signals, but are otherwise unable to traverse portions of theskull in X and Y directions. All existing semi-automated methods requirea knowledgeable user to place the robotic mechanism on an existingwindow. If such an existing mechanism is not placed on an existingwindow, useful data will not be returned. Some existing two degree offreedom mechanisms will not always find a signal, when they do, it oftentakes a trained technician to determine the location of appropriatewindows and the best signals. Further, some existing mechanisms are notcapable of constructing a map of blood vessels in the brain. As such,there exists a need to develop a fully automated robotic system thatdoes not require user feedback to locate appropriate windows and iscapable of constructing a map of blood vessels in the brain more quicklythan current solutions.

SUMMARY

According to some embodiments, there is provided a head-mounted medicaldevice that can automatically search, locate and acquire a stable CBFVwaveform from any human being's temporal window, independent of his orher age, size, shape, or demography in an acceptable period of time(e.g., under five minutes). By automating the process of acquiring TCDsignals, or other sensory modalities, using a robotic transducerpositioning system that uses prior knowledge of the head anatomy forrapid signal discovery and locking, embodiments can vastly expand theclinical utility of TCD to settings outside of hospitals. Furthermore,embodiments can function with existing TCD systems. Embodiments enableon-site, rapid diagnosis of TBI.

According to various embodiments, there is provided a device, includinga processor configured to control a robotic system to autonomouslyposition a transducer at a plurality of locations adjacent a subject'sskull and to autonomously locate a window on the subject's skull withinwhich an artery can be located, from which artery a signal can bereturned to the transducer, the signal having an energy level exceedinga predefined threshold. In some embodiments, the processor is furtherconfigured to cause the robotic system to autonomously locate within thewindow an ultrasonic signal representative of blood flow within anartery, the signal having an energy level exceeding a predefinedthreshold. In some embodiments, the processor is further configured torecord in a database a plurality of locations of the transducer as therobotic system autonomously positions the transducer. In someembodiments, the processor is further configured to record in a databasea plurality of energy levels of signals as the robotic systemautonomously positions the transducer. In some embodiments, theprocessor is further configured to record in a database a plurality oflocations of the transducer as the robotic system autonomously positionsthe transducer. In some embodiments, the processor is further configuredto record in a database a plurality of energy levels of signals as therobotic system autonomously positions the transducer. In someembodiments, the processor is further configured to execute a searchalgorithm stored on non-transitory computer readable media. In someembodiments, the device further includes a robotic mechanism configuredto move the transducer in multiple axes, and the search algorithm isfurther configured to control pan, tilt, and Z axis positions of therobotic mechanism. In some embodiments, the device includes a databaseof seed points stored on non-transitory computer readable mediaaccessible by the processor, which database of seed points is used bythe processor. In some embodiments, the device further includes adatabase of previously measured locations stored on non-transitorycomputer readable media accessible by the processor, which database ofpreviously measured locations is used by the processor. In someembodiments, the processor is configured to execute a search algorithm,the search algorithm being configured to use dynamic dwell time at aplurality of locations searched. In some embodiments, the robotic systemfurther includes a five degree of freedom robotic mechanism. In someembodiments, the robotic system further includes a five degree offreedom robotic mechanism configured to move the transducer in multipleaxes simultaneously. In some embodiments, further includes a roboticheadset within which the transducer is mounted. In some embodiments, theprocessor is further configured to cause the robotic system to build avascular map of the brain inside the subject's skull. In someembodiments, the transducer is an ultrasound probe.

According to various embodiments, there is provided a robotic imagingdevice, including a transducer, a processor in communication with thetransducer, the processor configured to receive and process data fromthe transducer, a robotic mechanism controlled by the processorconfigured to move the transducer to scan for and locate a window in askull of a subject, and wherein the processor is configured toautonomously control the robotic mechanism to search for and locate aTCD signal within a window in the skull of the subject, said TCD signalhaving an energy level exceeding a predefined threshold. In someembodiments, the processor is further configured to execute a searchalgorithm stored on non-transitory computer readable media. In someembodiments, the processor is further configured to execute a searchalgorithm stored on non-transitory computer readable media, which searchalgorithm employs dynamic dwell time at a plurality of search locations.In some embodiments, the robotic mechanism is further configured to usea visual window guide used for initial registration. In someembodiments, the robotic mechanism is further configured to move in atleast two axes simultaneously. In some embodiments, the roboticmechanism is further configured to include a five degree of freedomrobotic mechanism configured to move the transducer in multiple axessimultaneously. In some embodiments, the robotic mechanism is furtherconfigured to include a six degree of freedom robotic mechanism. In someembodiments, the robotic mechanism is further configured to include atleast a four degree of freedom robotic mechanism. In some embodiments,the device further includes a feedback mechanism used to adjust locationdue to subject movement.

According to various embodiments, there is provided a method forlocating an artery in a subject's brain, including the steps ofcontrolling a processor to autonomously locate a window of a subject'sskull, and within the window of the subject's skull, to autonomouslylocate a first ultrasonic signal representative of blood flow within anartery, the first ultrasonic signal having an energy level exceeding apredefined threshold. In some embodiments, the method further includes astep of moving and autonomously locating a second signal representativeof blood flow within an artery, the second signal having an energy levelexceeding a predefined threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinafter and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1A is a perspective view of an ergonomic headband.

FIG. 1B is a view showing the ergonomic headband on a head.

FIG. 1C is an elevation view showing the ergonomic headband on a head.

FIG. 2 is a side view of an exemplary TCD headset worn by a patient.

FIG. 3A is a perspective view of a TCD headset worn by a patient.

FIG. 3B is a perspective view of a TCD headset worn by a patient.

FIG. 4A is an elevation view of a TCD headset with the housing removedworn by a patient.

FIG. 4B is an elevation view of a TCD headset with the housing removedworn by a patient.

FIG. 5 is perspective view of a TCD headset worn by a patient containingmultiple straps.

FIG. 6 is perspective view of a wired TCD headset worn by a patient.

FIG. 7 is perspective view of a wireless TCD device worn by a patient.

FIG. 8 is a system diagram of a TCD system.

FIG. 9 is an elevation view of a transducer and illustrates admittancecontroller to control force.

FIG. 10 is a perspective view of a TCD transducer holder.

FIG. 11 illustrates a discovery platform including a small robotattached to an ergonomic head band.

FIG. 12 illustrates a grid search pattern.

FIG. 13 illustrates a grid search pattern.

FIG. 14 illustrates overlapping volumes in a target area.

FIG. 15 illustrates overlapping volumes in a target area.

FIG. 16A illustrates TCD sensor placement for insonating the middlecerebral artery (MCA).

FIG. 16B illustrates TCD sensor placement for insonating the middlecerebral artery (MCA).

FIG. 16C illustrates TCD sensor placement for insonating the middlecerebral artery (MCA).

FIG. 17 illustrates temporal window landmarks and limits.

FIG. 18A illustrates example TCD locations.

FIG. 18B illustrates example TCD locations.

FIG. 19A illustrates the F, A, M, P locations on the temporal window ofa skull.

FIG. 19B illustrates insonation of the F, A, M, P locations on thetemporal window of a skull.

FIG. 19C illustrates various locations that can be insonated on a skull.

FIG. 19D illustrates a six degree of freedom robot arm with a probe ortransducer.

FIG. 19E illustrates a six degree of freedom robot arm mounted with aportable workstation.

FIG. 19F illustrates a six degree of freedom robot arm insonating thetranstemporal window.

FIG. 19G illustrates a six degree of freedom robot arm insonating thetransorbital window.

FIG. 19H illustrates a six degree of freedom robot arm insonating thesubmandibular window.

FIG. 19I illustrates a six degree of freedom robot arm insonating thesuboccipital window.

FIG. 20 illustrates a data-driven search algorithm for automatic signalacquisition.

FIG. 21 illustrates a stack-search algorithm.

FIG. 22 illustrates a CBFV spectrum.

FIG. 23A illustrates a power M-mode Doppler display.

FIG. 23B illustrates a schematic of anatomy of arteries in the brain.

FIG. 24 illustrates CBFV samples for a blood vessel.

FIG. 25 is a diagram of a virtual support structure for manipulating amedical probe, according to an exemplary embodiment.

FIG. 26 is an perspective view of a medical probe and a gimbalstructure, according to an exemplary embodiment.

FIG. 27 is a perspective view of a two-link revolute support structurefor the medical probe of FIG. 26, according to an exemplary embodiment.

FIG. 28 is front elevation view of the support structure of FIG. 27.

FIG. 29 is a right side elevation view of the support structure of FIG.27.

FIG. 30 is a perspective view of a prismatic support structure for themedical probe of FIG. 26, according to an exemplary embodiment.

FIG. 31 is front elevation view of the support structure of FIG. 30.

FIG. 32 is a right side elevation view of the support structure of FIG.30.

FIG. 33 is a schematic front view diagram of the support structure ofFIG. 27.

FIG. 34 is a schematic front view diagram of the support structure ofFIG. 30.

FIG. 35 is a flowchart of a method for determining the input force, ortorque, for an actuator, according to an exemplary embodiment.

FIG. 36 is a perspective view of a 5-bar parallel mechanism(revolute-revolute) support structure for the medical probe of FIG. 26,according to an exemplary embodiment.

FIG. 37 is front elevation view of the support structure of FIG. 36.

FIG. 38 is a right side elevation view of the support structure of FIG.36.

FIG. 39 illustrates a hybrid position-force admittance controller.

FIG. 40 illustrates a top perspective view of a spring loaded probe in asupport structure with four actuated degrees of freedom as well as onepassive degree of freedom.

FIG. 41 illustrates a front perspective view of a spring loaded probe ina support structure with four actuated degrees of freedom as well as onepassive degree of freedom.

FIG. 42 illustrates a cross-sectional view of a spring loaded probe in asupport structure with four actuated degrees of freedom as well as onepassive degree of freedom.

FIG. 43 illustrates a front perspective view of a five actuated degreesof freedom prismatic support structure for a medical probe, according toan exemplary embodiment.

FIG. 44 illustrates a rear perspective view of a five actuated degreesof freedom prismatic support structure for the a medical probe,according to an exemplary embodiment.

FIG. 45 illustrates an exploded perspective view of a five actuateddegrees of freedom prismatic support structure for the a medical probe,according to an exemplary embodiment.

FIG. 46 illustrates a front perspective view of a remote center ofcompliance probe device according to various embodiments.

FIG. 47 illustrates a rear view of a remote center of compliance probedevice according to various embodiments.

FIG. 48 illustrates an exploded view of a remote center of complianceprobe device according to various embodiments.

FIG. 49 illustrates a top view of a first plate of a remote center ofcompliance probe device according to various embodiments.

FIG. 50 illustrates a top view of a second plate of a remote center ofcompliance probe device according to various embodiments.

FIG. 51 illustrates a free body diagram including a remote center ofcompliance probe device according to various embodiments.

DETAILED DESCRIPTION

In the following description of various embodiments, reference is madeto the accompanying drawings which form a part hereof and in which areshown by way of illustration specific embodiments in which theembodiments may be practiced. It is to be understood that otherembodiments may be utilized, and structural changes may be made withoutdeparting from the scope of the various embodiments disclosed in thepresent disclosure.

Some of the likely beneficiaries of this technology include emergencyroom, acute care centers, general practice physicians, first responders,and other health care professionals (athletic trainers). They willbenefit from the ability to rapidly diagnose and monitor head injury.

For first responders and untrained technicians, various embodimentsprovide a robotic TCD system or robotic mechanism that is fullyautomated, enabling accurate and rapid diagnoses and management TBIs,strokes, and other neurological conditions. Embodiments may leverageother technologies for machine learning algorithms that enableneurological conditions diagnoses based on subtle CBFV waveform changes.Additionally, embodiments can automate search methods traditionallycompleted by trained sonographers, making these methods easily availableat the point of care.

According to various embodiments, there is provided a head-interfacingmedical device that can automatically search, locate and acquire astable CBFV waveform exceeding a predefined quality threshold from anyhuman being's temporal window, independent of his or her age, size,shape, or demography. According to other embodiments, other acousticwindows may also be used. Embodiments may employ the use of force andtorque sensors to maintain appropriate contact force that maximizessignal quality. Embodiments may also employ the use of amachine-learning algorithm to emulate the expertise of a trainedtechnician in locating the insonated vessel.

In order to locate and insonate a vessel of interest, the position andorientation of a transducer may be described by five coordinates, ordegrees of freedom (DOFs): three translation coordinates (x,y,z), andtwo rotational coordinates (pan and tilt). For automatic transducerplacement, all five coordinates may be independently controlled. Whilethis specification frequently mentions a transducer, in general, thetechniques and devices herein specifically described as using atransducer could also be employed in various embodiments using a probeor sensor probe. Several approaches have been attempted or are beingdeveloped to simplify TCD signal acquisition. Briefly, these can bedivided into fully automated or semi-automated TCD signal acquisition.

Semi-Automated TCD Signal Acquisition:

Several methods have been developed to assist or aid a TCD technician inlocating and maintaining a stable signal. One of these is the PowerMotion-Mode Doppler (PMD). A color-coded display of all flow signalsdetectable at a given position and direction of the transducer in realtime is provided by PMD. The major advantages of PMD are thattranscranial windows can be easily found and maintained by aultrasonographer and it facilitates vessel identification using depthand direction of flow. Although this technique is now a routine featureof most modern TCD systems, this technique still requires an expertsonographer for operation.

Another notable product for semi-automation of signal acquisition is aheadband using robotics to implement a limited number of active degreesof freedom. The headband features two degrees of freedom that arerobotically controlled (pan and tilt) and three degrees of freedom—x andy translations and z positioning manually, using mechanical fixtures.The two angular automatic DOFs scan angles of ±15 degrees to locate theoptimal angles of insonation, resulting in a semi-automated windowdiscovery and vessel identification process. Such transducer positioningsystems with two automatic DOFs and with control of the TCD insonationdepth as a third DOF, can place a sample volume within the brain at aCartesian location (x,y,z). With only three total degrees of freedom,the orientation of the sample cannot be specified. Therefore, the angleof incidence to the blood flow cannot be set so there is no guarantee ofthe signal strength. The angle can only be adjusted by the user manuallymoving the transducer.

Fully-Automated TCD Signal Acquisition:

Probes have been developed that consist of a two-dimensional array oftransducers (two dimensional phased array transducer). An advantage ofthis technology is that an ultrasound insonation beam can beelectronically steered in translational and angular degrees of freedomto discover the insonation window and the vessel of interest. However,the method is only usable for the long-term continuous monitoring ofCBF, as it has a setup time of greater than 30 minutes.

In various embodiments, there is provided a five degree of freedom (DOF)kinematic mechanism that fully automates TCD sensor position andorientation, evaluation of the temporal window quality, and canrediscover the temporal window even after complete loss of signal. Whilethis specification frequently discusses Transcranial Doppler (TCD)probes, in general, the techniques and devices discussed hereinspecifically described as using TCD can also be employed in variousembodiments using probes for methods such as ultrasound, transcranialcolor-coded sonography (TCCS), phased arrays well as well as other knownultrasound energy modalities. Additionally, other techniques that useprobes that emit or receive energy in the electromagnetic spectrum suchas functional Near-Infrared Spectroscopy (fNIRS) or EEG can also beemployed. To automate window discovery and vessel identification, acomputer controls the mechanism to translate and reorient the transduceralong the surface of the head until a candidate signal is located. Thecomputer is in communication with the transducer and receives andprocesses data from the transducer. Once located, the transducer is thenreoriented to increase signal strength. Accordingly, embodiments canperform functions an expert sonographer cannot, and allows the use ofTCD outside of specialized clinical settings. In some embodiments, anautomated system makes TCD a viable option for smaller neurologicalclinics as well as primary care physicians. Some embodiments provideclinicians the ability to diagnose neurological conditions that mayotherwise go untreated until a patient is symptomatic, as well asmonitor pathologies such as sickle-cell anemia, that would otherwiserequire visits to an imaging center—ultimately reducing health systemcosts and bringing better standards of care to patients.

Accordingly, some embodiments provide a robotic system for automaticallyperforming TCD scans. In some embodiments, the robotic system ormechanism may consist of a five degree-of freedom or sixdegree-of-freedom TCD transducer positioning system with motion planningdriven by prior domain expertise given knowledge of the human anatomy.In some embodiments, the positioning system can translate in x and yaxes to locate the window in translational axes, and in the z axis withboth force and position feedback control to both position and maintainthe appropriate force against the human skull to maximize signal qualityby maintaining appropriate contact force. Two angular degrees of freedom(pan and tilt) are be used to maximize normal insonation of the bloodvessel to maximize velocity signal. In some embodiments, the motionplanning and vessel location may be driven by a machine-learningalgorithm in order to locate the optimal TCD signal, or a TCD signalwith an energy level exceeding a specified or predefined threshold. Insome embodiments, the algorithm drives the search trajectory whilesimultaneously analyzing the blood flow velocity and motion-mode(M-mode) information from the TCD sensor to identify a candidate for theTCD window.

In some embodiments, the system includes a small robot holding a TCDtransducer attached to an ergonomic headband. The robot's five degreesof kinematic freedom allow for the positioning and orientation of theTCD transducer. In some embodiments, each degree of freedom is driven bya motor with an optical encoder, hall effect, or other sensor to provideposition feedback. Three degrees of freedom enable the transducer to beplaced against the head and to slide along the skin in both up and downand side to side directions. The remaining two degrees of freedomimplemented with gimbal are used to adjust the orientation of thetransducer, which changes the direction of the ultrasound beampenetrating into the skull. FIG. 2 shows a side view of an exemplary TCDheadset 50 worn by a patient.

Embodiments also provide a fully-automated robotic device for TCD windowdiscovery and signal acquisition. An automated TCD transducer mayaccomplish two technical objectives: 1. Control the position,orientation and motion of the transducer exploring the surface of thehead while applying an appropriate level of force; 2. Automate TCDwindow discovery and signal lock by implementing a search and signalprocessing algorithm that controls the transducer while interpreting theTCD sensor information to confirm discovery of the TCD signal andoptimizing the signal strength. In some embodiments, positioninformation is recorded and stored in a database. Furthermore,embodiments may correlate the signal to specific vascular anatomy (e.g.,middle cerebral artery (MCA) vs posterior cerebral artery (PCA)), andmay perform vascular mapping and vessel walking.

TCD sonography requires placement of the ultrasound transducer to thesubject's head and moving the transducer while maintaining contactduring both signal discovery and until the end of the data collection.Therefore, some embodiments control the transducer position and motionto enable the overall innovation of automatic TCD discovery and signallock. In some embodiments, a robot automatically positions the deviceagainst the head and slides the transducer along the surface whileapplying sufficient force to maintain contact, without hurting subject.A technical challenge is to maintain the transducer nominally normal tothe head during the surface exploration, with only approximate knowledgeof the surface orientation, while controlling for applied force.

In some embodiments, the second technical objective integrates the TCDsensor information with robotic transducer motion to locate the TCDwindow, identify a signal, and reposition the transducer in order tomaximize the signal strength during data collection. In someembodiments, a search algorithm controls both robotic transducer motionand the TCD transducer settings and data output. In some embodiments,the algorithm plans a transducer search trajectory while simultaneouslyanalyzing the blood flow velocity and M-mode information from the TCDsensor to identify a candidate for the TCD window. Once the signal isacquired, the algorithm will direct the robot to reposition and reorientthe transducer to minimize the Doppler angle, thereby increasing thesignal magnitude. Various embodiments implement several types of searchalgorithms (e.g., a grid search of the temple area of a human subject).Some embodiments implement other algorithms with the goal of reducingsignal acquisition time. Some embodiments of these other algorithmsnon-linear search motions, prediction based machine learning algorithms,or a combination of algorithms.

In some embodiments, there is provided a headset capable of diagnosing,monitoring, and treating a number of neurological conditions. In someembodiments, the headset utilizes ultrasound for the insonation of themajor conducting arteries or veins of the brain; however, the technologyis not limited to insonation of the cerebral vasculature as it could beused to insonate specific regions of the brain while utilizing thevasculature as a landmark (once it is known where the blood vessels are,the location of everything else in the brain is known). In someembodiments, the headset may include various sub-components or features,including:

Automatic Transducer Placement—

In some embodiments, the system is placed on the head of the individual.In some embodiments, the system that interfaces with a head isimplemented in a headset, but as will be discussed below, otherembodiments exist as well. Once this placement has been accomplished,the ultrasound probes (or other transducer technology) come into contactwith the skin.

Surface Alignment—

In some embodiments, the transducer is correctly aligned with thesurface of the skin to be useful.

Transducer Force Control—

In some embodiments, in addition to surface alignment, a control offorce of the transducer on the skin of a subject or patient is providedsuch that there is enough force to maintain contact, yet not too much tocause damage or discomfort to a subject or to the probes. In someembodiments for the automatic transducer placement mechanism, atransducer force control mechanism is built in.

Window Discovery—

In some embodiments, once the transducer is on the skin, the automatedsystem identifies or finds the section of bone that is thin enough forthe ultrasound energy to pass through in able to monitor the blood flow.The section is known as the acoustic window.

Signal Optimization—

In some embodiments, when the system has identified the correct locationon the skull and has positioned the ultrasound transducer toassess/measure cerebral blood flow, the system then optimizes the bloodflow signal using a number of different inputs, such as, for example,orientation, signal quality, sound, depth, or intensity. Thisoptimization may be accomplished for one depth or multiple depths.

Vascular Mapping—

The cerebral vault has a number of major conducting arteries (i.e.Circle of Willis arteries) that can be insonated using embodiments. Insome embodiments, once the signal is optimized, embodiments can optimizethe signal automatically for all vessels and build a vascular map of thesubject's brain.

Clinical Indications—

Some embodiments described herein can be used for a number of differentneurological conditions including TBI, stroke, dementia, vasospasm, andothers impacting cerebral blood flow. These uses include diagnosis,monitoring, and treatment.

Diagnosis—

Some embodiments measure small changes in cerebral blood flow andcerebral blood flow regulation. Results can be obtained to diagnosesevere TBI (intracranial pressure), mild TBI (concussion), and specificstrokes including large vessel occlusion and SAH.

Monitoring—

Some embodiments can be used to determine how a neurological conditionchanges over time, e.g., over 12 hours for TBI or concussion or yearlycheckups to diagnose/monitor dementia over a lifetime.

Treatment—

Some embodiments can provide the use of ultrasound to break up clots orstimulate specific regions of the brain.

In some embodiments, the TCD signal is acquired using an ultrasoundtransducer that is placed against temporal window of a human subject'shead. Each measurement may include positioning of the transducer inthree translational and two rotational or orientation degrees offreedom. The measurement may include first scanning the temporal windowof each subject to find the optimal TCD signal and then maintaining thesignal lock, e.g., for up to 20 minutes, to collect sufficient data tomake a diagnosis. As there are two temporal regions on a human head,each potentially consisting of a plurality of access windows, someembodiments perform bilateral scans.

In some embodiments, a robotic scanning system is provided whichincludes an electromechanical apparatus to automate scans bilaterally.The robotic scanning system enables operation and use of TCDultrasonography by a lay user. It also allows optimization of the scanprotocol, and makes signal acquisition reliable and repeatable.

In some embodiments, the robotic scanning system subsystem has at leastthree embodiments: commercial, consumer, and military. The commercialversion is well-suited for use by healthcare professionals and inprofessional/collegiate athletics. The consumer version is well-suitedfor use in high school and youth athletics but may be used in healthcareand pro/collegiate athletics if it meets the all requirements. Themilitary version is well-suited for military field hospital use.

External Control Software/Firmware Application as a User:

Some embodiments control the movement and orientation of a TCDtransducer with five degrees of freedom (x, y, z, pan, and tilt) so thatthe system is able to reliably detect MCA, PCA and anterior cerebralartery (ACA) arteries. In controlling the Cartesian degrees of freedom,an embodiment computes the inverse kinematics of the mechanism in orderto command the joint positions. Some embodiments command the firmware tomove the mechanism smoothly between several Cartesian configurationsusing a limited set of time-space interpolation points.

In some embodiments, robotic motors work together to increase the robotspeed. In some embodiments, rather than simply moving along the x and yaxes in a serial fashion, the robot moves the transducer along the x andy axes simultaneously to minimize the time to get to a new position. Forexample, if a robot can move along the x axis with a velocity v, and canmove along the y axis at a velocity v, it could move to a diagonal pointat a rate of v*√{square root over (2)}, which is more than 40% fasterthan moving serially in only the x or y directions. In some embodiments,speed will further be increased if movement is made in the pan and tiltdirections simultaneously.

In some embodiments, an application program interface (API) exists froma software application to command positions that does not necessarilyupdate at the servo rate. Some embodiments query the status of thefirmware. In some embodiments, the software/firmware API includes afirmware status update. In some embodiments, a firmware applicationscans enough temporal surface area so that the system is able toreliably detect MCA, PCA and or ACA for a subject. In some embodiments,the parameters of the scan are: Area size: no less than 55 mm across (xaxis) by 30 mm down (y axis); Motion into the head (z axis) issufficient to clear the head to ease removal of the device. In someembodiments, a software application controls scanning of the temporalsurface of a patient or subject in less than two minutes. In someembodiments, translation speed of the sensor is not less than 7.5 mm/s.

In some embodiments, a firmware application controls the Cartesianmovement of the TCD in the x,y,z axes with a precision and resolution of1 mm to obtain TCD data, and it allows positioning of a 2 mm sample sizeTCD beam within a 4 mm vessel diameter. In some embodiments, precisionand resolution increase to perform vascular mapping. In someembodiments, a firmware application orients the TCD transducer over alarge enough range that the system is able to reliably detect MCA, PCAand ACA over a variety of head shapes. In some embodiments, pan and tiltare capable of rotating a minimum of ±30 degrees, and increases toaccount for anatomical differences of temple interface to transducer.

In some embodiments, a firmware application orients the TCD transducerwith a precision and resolution of 0.1 degrees to obtain TCD data. Thisprecision greatly exceeds the performance of an experienced human userand could only be achieved with the precision of a robotic system. Insome embodiments, a firmware application puts adequate and constantpressure with TCD sensor on patient's head to be able to acquire a highfidelity TCD signal.

In some embodiments, a software application prevents mechanical motionfrom interfering/coupling with the ultrasound signal, to allowcollection of cleaner data for an algorithm to analyze TCD signals withhigher reliability. In some embodiments, a software application providesbilateral scanning, to make algorithms more efficient, with correctkinematics. In some embodiments, two mechanisms are used. In someembodiments, a single mechanism is used and it swaps to either side ofthe head for access to either of the temporal windows.

In some embodiments, a minimal amount of gel is necessary to enable TCDsensing, so as to prevent gumming up the mechanics. In some embodiments,the gel is capable of being cleaned from the machine easily. In someembodiments, the system actively maintains the TCD signal for 20 minutesor more after acquisition in order to complete a breathing protocol.Maintaining the signal may involve actively repositioning the TCD systemto strengthen the signal due to patient motion. Some embodiments canmaintain the signal for 6 hours or more.

A. Headset Design

FIGS. 1A-1C depict a Transcranial Doppler (TCD) device according tovarious embodiments. FIG. 2 depicts a TCD headset 50 according tovarious embodiments. FIGS. 3A-3B depict a TCD headset 100 according tovarious embodiments. FIGS. 4A-4B depict a TCD device 100 according tovarious embodiments. FIGS. 5-7 depict variations of TCD headsets 163according to various embodiments.

FIGS. 1A-1C show an automated TCD headset 40 having a display screen 42on the front thereof. More particularly, the headset 40 includes dualultrasound probes 44 on the sides and a headband 46 that extends aroundthe front so as to connect the two probes. As seen in FIGS. 1A-1C theheadset 40 fits over the cranium of a patient with the probes 44 locatedat either temple. The probes 44 include TCD scanners therein that canauto locate the MCA, ACA, PCA or other arteries. Desirably, the headband46 may be elastic or adjustable in nature and enables the headset 40 tofit snugly over the front of the head of a variety of different headsizes so that the inner face of the probes 44 makes good contact withthe temples. A lubricating gel is preferably used to improve acoustictransmission.

Although not shown for the sake of clarity, power supplies, either inthe form of batteries, or power supplies that operate based on readilyavailable convenience outlets or other available electrical current areused to electrically power all components that normally requireelectrical power, such as transducers, motors, computers and processors,robot arms, electrical circuit boards, displays, and the like.

FIG. 2 is a side view of another exemplary TCD headset 50 worn by apatient and having a forehead strap 52, a rear strap 54, and a cranialstrap 56. The straps 52, 54, 56 help secure the headset 50 on the head,and in particular ensure good contact of a pair of reciprocatingultrasound scanners 58 with either temple. The TCD scanners 58 mount forreciprocal forward and backward rotation, as indicated by the movementarrows, to a junction member 60 at the intersection of the three straps52, 54, 56. In one embodiment, the TCD scanners 58, which incorporatetransducers or probes, rotate about 60° in each direction about a z axisperpendicular to the x,y scan plane. Although not shown for the sake ofclarity, a small motor within the junction member 60 enables movement ofthe scanners 58.

The system of the three straps 52, 54, 56 is effective in holding theheadset 50 in place. The cranial strap 56 includes a Velcro break foradjustability, the rear strap 54 is desirably elastic, and a pair oftightening knobs 62 on each junction member 60 and a tightening knob 64at the middle of the forehead strap 52 enable fine adjustment of theposition of the scanners 58 for X-Y calibration. The cranial strap 56helps limit migration of the headset 50 once secured due to movement ofthe jaw and associated muscles.

In some embodiments, a cable 66 may be attached to the junction members60 for connection to a control unit such as computer 67, a tabletcomputer (not shown for clarity), or any other type of computing device,or the system may communicate wirelessly with a computing device. Thecomputer 67, or other connected computing or processing device is incommunication with and provides processing to receive and process datareturned from TCD Scanners 58.

Each TCD scanner 58 desirably includes an injection port 68, preferablyformed by an indent leading to a channel, for introduction of alubricating gel to the inside contact surfaces. This injection port 68helps reduce a messy application of the gel. In a preferred embodiment,the TCD sensor on the inside of each scanner 58 may be displaced in thez direction, or toward and away from the temple, to optimize acousticcontact. In some embodiments, headsets are capable of being cleaned ofall ultrasonic coupling gel following use. Preferably, wipes or othersuch devices are used to protect the mechanism from accumulation offoreign matter within the mechanism. Materials selected withstandcleaning with water, isopropyl alcohol, and other cleaning agentsroutinely used in the doctor's office and clinical setting.

FIG. 3A is a perspective view of an exemplary TCD headset 100 positionedon soft mounting feet 102 on the side of a patient's head. Two sizes ofpatients' heads, small S and large L, are shown in contour lines toindicate the range of adjustability of the headset 100 for differentsizes of patients. An outer housing 104 is shown in phantom to visualizeinternal components of the headset 100.

FIG. 3B shows the outer housing 104 against a profile of the wearer'shead for clarity, and also shows a second headset 100 on the oppositeside of the patient's head connected to the first set by straps 110. Insome embodiments, each headset 100 has a plurality of the mounting feet102 which resemble small suction rings to cushion the sets against thehead and also provide some spacing between the head and the outerhousing 104. In some embodiments, there are three mounting feet 102 oneach side, as shown in FIG. 4A. The headsets 100 are anchored bytensioning the straps 110. There may be one forehead strap 110 as shown,or also one around the rear and even one over the cranium, as wasdescribed above in connection with FIG. 2.

With reference to FIGS. 4A and 4B, side elevational views of anembodiment of the TCD headset 100 of FIGS. 4A and 4B are shown with theouter housing 104 removed. Within the housing, a TCD scanner 120 mountson a carriage 122 that slides on a pair of diagonal rails 124. Thecarriage 122 includes a small motor 130 that turns drive gears that meshwith small teeth 134 along both rails 124. The motor 130 may becontrolled remotely or by wires, and the carriage 122 thus may be moveddiagonally along the rails 124.

In some embodiments, the TCD scanner 120 mounted on the carriage 122thus may be moved over the temple area of the subject. In someembodiments, the headset 100 can desirably scan an area of about 2square inches as indicated by the dashed square area 150. To cover theentire area 150, the upper ends of the rails 124 pivotally attach to aframe member 152 that translates laterally along a generally horizontalpath. More specifically, a pivot point 154 on the frame member 152connects to a translating rod 156 that may be moved by a cylinder 158 ina piston/cylinder relationship. Alternatively, the cylinder 158 maycontain a small motor which engages the end of the rod 156 opposite thepivot point 154 and translates it laterally. There are several ways toaccomplish this movement, and each is controlled along with movement ofthe carriage 122 for coordinated two-dimensional movement of the scanner140 in the x,y plane over the target area 150.

In addition, in some embodiments, the robotic arm encompassing thescanner 140 mounted for movement on the carriage 122 has a z axisdisplacement device actuated by a stepper motor 160. The robotic arm isfurther equipped with a pressure sensor (not shown) that maintainssufficient pressure of the scanner 140 against the skin for consistentsignal quality. This pressure sensor is a feedback mechanism used toadjust location due to subject movement. This constant pressureaddresses variability issues associated with patient movement and TCD.

In some embodiments, translational motion along the x,y,z axes and thepan and tilt directions or orientations are accomplished through use ofmotors 160 driven by a local motion control unit 162. The motion controlunit 162 may comprise a microcontroller with memory and a CPU programmedto monitor and control the motors 160, as described in more detailbelow. In some embodiments, servo feedback is provided to assure thatthe desired position has been achieved. The servo feedback signal takesthe form of a reverse EMF or encoder signal provided to the motorcontrol unit 162. In some embodiments, instead of placing a programmedmicrocontroller in the headset co-located with motor 160, as shown inFIG. 2 and FIG. 6, a cable 66 may connect the headset with a computer67, or the headset may communicate wirelessly to a computer 67 that isprogrammed to move the motors 160 and monitor the information returnedfrom a TCD transducer (not shown for clarity) located within theheadset.

Command Set:

In some embodiments, X,Y,Z axes and pan and tilt direction movement willbe controlled via an appropriate processor or microprocessor. In someembodiments, a command for movement along any axis will be in the formof a signed integer number indicating the number of step increments tobe moved along each axis.

FIG. 5 shows a headset 163 with multiple straps 164, 165, 166 to allowfor a snug fit. A unit that can adjust to several head sizes isimportant for wide-spread adoption. If the head mount does not fitcorrectly the TCD probes cannot acquire the optimal signal. Thedisclosed design addresses this concern separating the “anchoring” ofthe headset and the robotic mechanism. This design allows the user tofit the headset on any sized head with no impact on the ultrasoundmechanism to reach the signal.

FIG. 6 shows a headset 163, connected via a cable 66 to a computerdisplay 167 that may be used to input information from the patient orsubject and to display information obtained from the scan of the patientor subject. FIG. 7 shows a headset 163 communicating wirelessly with adisplay 167 that may be used to input information from the patient orsubject and to display information obtained from the scan of the patientor subject. The headset 163 and display 167 may communicate wirelesslyusing wireless methods of communication known to those skilled in theart, such as Wi-Fi, Bluetooth, Li-Fi, cellular communicationtechnologies, and other known methods of radio communication.

In certain embodiments, the systems and methods described could be usedfor the diagnosis of mild and moderate TBI where there is no increase inICP. The underlying physiology is different; however, the core analysisis the same. The cerebral hemodynamic changes following a mild TBI arewell documented by several studies. The physiologic origin of thesechanges range from regional blood flow variations owing to increasedmetabolic demand in certain regions of the brain to variations in CBFdue to disruptions in the cerebral vasculature or the brain itself (suchas decreased compliance due to high intracranial pressure (ICP).

B. Automatic Transducer Placement

FIGS. 8-11 illustrate various TCD systems and devices capable ofautomatic transducer placement.

Integrated System Framework for Automatic TCD Sonography—

As shown in FIG. 8, in some embodiments, an automated TCD system 201comprises a robot arm 190, also referred to as a redundant manipulator,that provides robotic positioning, transducer holder 204, transducer 20,with force sensor 206, TCD driver board 208, and algorithm controlcomputer 210. A preferred device used to position and orient thetransducer is a commercially available six degree of freedom UniversalRobotics, UR3 tabletop robot arm 190. This robot arm 190 providessufficient kinematic precision, has been certified for use around humanbeings in its workspace, and has settable safety levels to limitvelocity and impact forces. It also has additional degrees of freedom.These characteristics address safety concerns to allow use with humansubjects. A probe or transducer 20, that may be a Spencer TCD probe, ismounted onto a transducer holder 204, called an “endeffector.” Theendeffector mounts to the end of the robot arm 190 and has an axialforce sensor 206 to monitor directly force applied by the robot arm 190to the surface being scanned. The force sensor 206 sends force sensorinformation 212 to the robot arm 190. This force sensor 206 serves bothto ensure that enough contact force is made between the transducer 20and the surface being scanned, but is also a second measure of safety toprevent overloading of contact forces. In some embodiments, the probedriver board 208 connects to the transducer 20 and provides electronicsto send power 214 to the probe to emit ultrasound energy and process thereturned sensor output signal 216.

In some embodiments, the control computer 210 connects to andcommunicates with the robot arm 190 controller 220 via TCP/IPcommunication 218 and to the probe driver board 208 by USB 222. Therobot arm 190 provides information 224 about such things as its currentposition, velocity, estimated forces applied to the endeffector, customsensor readings, and other status information to controller 220, whichis then communicated via TCP/IP 218 to the control computer 210. Theprobe driver board 208 USB 222 interface provides a method of setting uptransducer 20 parameters and operation, such as depth, and processesdata to produce information such as, but not limited to, the velocityenvelope. The control computer 210 takes this information to execute theprobe search algorithm and to issue new robot arm 190 commands.Embodiments may also employ the use of a machine-learning algorithm toemulate the expertise of a trained technician in locating the insonatedvessel. In some embodiments, a control computer 210 autonomouslycontrols the transducer 20 scanning process, but in other embodiments, ahuman being may teleoperate the transducer 20 scanning process usingtechnology known to those of skill in the art, such as that used in theNeuroArm and DaVinci surgical robots.

Integration testing has shown that it is possible to maintain a 125 Hzcontrol loop over the entire system, which is fast enough to read alldata from the probe driver board 208, read all status data from therobot arm 190, update a signal processing and planning algorithm, andissue a new motion command to the robot arm 190 at its servo rate.

In some embodiments, a modular snake robot with more than six degrees offreedom is used instead of the UR3 to the redundant manipulator.

FIG. 9 illustrates admittance controller results control force withprecision. At left is shown transducer 20 mounted in probe holder 204,contacting force sensor 206, held by robot arm 190, to allow contactingand sliding over a flat surface. At right is shown the force outputcontrolled to a deadband range 223 of 2 to 10 N. FIG. 10 illustrates aTCD Transducer Holder: The transducer 20 is mounted on carriage 224 thatcan translate in x,y,z directions, while a gimbal mechanism (not shownfor clarity) allows for orientation changes in pan and tilt directions.FIG. 11 illustrates discovery platform 229 comprising: a small robot 225attached to an ergonomic head band 226. TCD Transducer electronics 227for processing TCD signals obtained from robot 225, and an output screen228 for displaying scan data are shown on the left side of the figure.

In some embodiments, TCD sensor positioning and orientation are achievedwith a robotic five degree of freedom (DOF) kinematic mechanism. For TCDapplications, the position and orientation of a transducer can bedescribed by five coordinates: three translation coordinates (x,y,z),and two rotational coordinates (pan and tilt). For automatic transducerplacement, all five coordinates can be independently controlled.

Some existing devices rely on an expert human user to manually translatethe transducer in x,y,z coordinates to the approximate location of thetemporal window against the head, and further control of the orientationto complete signal acquisition. After translational placement, somesemi-automatic devices are able to use two DOFs for orientation tofurther increase the signal strength. Control of orientation alone isinsufficient for transducer placement and temporal window discovery.

In some embodiments, the kinematic mechanism includes five motor degreesof freedom, Q={J1,J2,J3,J4,J5) (called motor or joint space) to affectfive degrees of freedom in position and orientation X={x,y,z,pan,tilt}(also called task space). The forward kinematics can be written as therelationship between motor coordinates and transducer coordinates:

X=fwd_kin(Q)

where fwd_kin is a function representing a series of equations based onthe mechanism design and typically analyzed by Denavit-Hartenbergparameters.

In some embodiments, placement of the TCD transducer can be specifiedvia the inverse kinematics with either an analytic inverse solution

Q=inv_kin(X)

or by using a numerical differential such as the Jacobian inversesolution

dQ _(cmd)(n)=J ⁻¹(X _(err)(n))

where J is the Jacobian, relating differential motion of the motors tothe differential motion of the transducer, X_(err)(n) is the transducerposition and orientation error at time n, and dQ_(cmd)(n) is thedifferential motor command at time n.

Some embodiments include enough DOFs to completely define the problem,i.e., 5 DOFs to define x, y, z, pan, and tilt. Another embodimentutilizes a depth setting for a 6th virtual DOF, creating a redundantmanipulator. This redundant manipulator enables the possibility for aninfinite amount of solutions. This embodiment increases possibilitiesfor how to place the sensor.

In some embodiments, after the device with the robot is placed on head(or head is placed into a device with robot), the robot moves thetransducer towards the patient while keeping the orientation of thetransducer normal to the surface of the head. Much of this process isestablished by using the kinematic knowledge of the device:

The Cartesian coordinates of the transducer is

X={x,y,z,pan,tilt}

Using the joint positions of each DOF, Q={q₁, q₂, q₃, q₄, . . . q_(n)}of the device and knowledge of the forward kinematics of the device, Xcan be computed as a function of the joint positions

X=fwd_kin(Q)

Using inverse kinematics to generate joint commands

dQ _(cmd)(n)=J ⁻¹(X _(err)(n))

Establishing transducer contact and seating against the head is notsimple because the exact orientation of the head relative to thetransducer is not known. Even if it is roughly in line with thetransducer, a small error will prevent the transducer from seating flushagainst the head. In some embodiments, the robot will attempt tomaintain the commanded orientation of the transducer with the programmedservo stiffness of the controller.

In some embodiments, for transducer contact and seating, instead oftrying to predict and control the exact position and orientation of thetransducer, the transducer's impedance is selectively controlled. Thiscontrol can be thought of as controlling an object's apparent stiffness,inertia, and friction, whether by mechanical design or software. In someembodiments, the orientation degrees of freedom of the transducer arecompliant so that they rotate against contact and seat the transducerflush with the head, while the translation degrees of freedom are stiffenough to move the transducer and keep it placed against the head. Insome embodiments, each of the directions have different impedances.

Software—Limiting Motor Torque and Motor Servo Stiffness:

In some embodiments, the simplest software solution limits the torqueapplied by each of the motors, and can have different limits forcreating different stiffnesses in different directions. This propertymakes the pan and tilt very compliant, while the translational aremoderately more stiff. The limitation is that the stiffnesses do notadjust as the orientation of the transducer changes. For example, as thetransducer changes orientation, the stiffness through the center of thetransducer is a combination of each of the X, Y and Z axis actuators,not just the Z actuator. Nominally stiffness through the transducershould be more compliant than the X, Y translational degrees of freedom.

Software—Task Space Impedance Control:

In some embodiments, the transducer orientation defines a localcoordinate system with the Z axis through the center of the transducer.Instead of manipulating the impedance of the transducer by adjustingmotor servo stiffness and torque limiting, the kinematics of the entirerobot sets the impedance of each of the five directions, X, Y, Z, pan,and tilt, local to the transducer's coordinate frame. The transducer canbe more compliant through the center line of the transducer and stillkeep in contact with the surface of the skin, but have local X and Ystiffness sufficient to control the transducer's location withprecision.

Hardware—Series Elastic Actuator:

In some embodiments, the impedance of the device can be altered byadding a compliant member into the mechanical design, either as a springelement into the motor or as a structural member of the robot. Eithermethod requires that the amount of deflection is measured in order tomeasure the exact position and orientation of the transducer. A serieselastic actuator has the benefit of being designed to an exactcompliance, and even have a damping element added, while avoidingcomputational nonlinearities and instabilities associated withprogramming the impedance.

Direct Sensing:

In some embodiments, the interaction force and torque can be controlledbetween the transducer and the head by placing a force/torque sensingbehind the transducer. Using that information the impedance of thetransducer can be programmed in software using closed loop control.

Indirect Sensing:—

In some embodiments, the force can be indirectly measured by monitoringthe applied current of the motor. Once taking into account thekinematics of the robot, the force/torque vector of the system can becomputed from the Jacobian: F=J^(T)T, where T is the vector of motortorques as predicted by the applied current to the motor.

In some embodiments, the automatic transducer placement system mayinclude different sensors. Although TCD probes are described, differentsensors may be utilized, such as, but not limited to, optical, radar,and the like.

In some embodiments, the automatic transducer placement system mayinclude a gel pad. For example, the pad of gel may be placed with aborder that the robot can identify, which could also serve as a methodfor transducer placement.

C. Window Discovery

Some embodiments that perform automatic window discovery do so usingmechanisms with four, five, six, or more degrees of freedom, whichinsonate at multiple depths and angles. These additional degrees offreedom and insonating at multiple depths and angles speed the processof locating appropriate window locations on the skull and mapping bloodvessels in the brain.

FIGS. 12-17 correspond to features of Window Discovery. FIGS. 12 and 13illustrate simple grid search patterns in which a transducer starts at astart location 1000, and moves from one location to the next in asliding direction 1002 to continuously sweeping over a grid in the X andY directions a snake like pattern until an end location 1004 is reached.Other embodiments use different search patterns. FIG. 14 illustratesoverlapping volumes 1006 a, 1006 b, 1006 c in a target area usingmultiple transducer positions 1008 a, 1008 b, 1008 c. Reorienting thetransducer positions 1008 a-c can sweep out a search volume. As shown inFIG. 15, overlapping search volumes 1006 a-c can be created byrepositioning the transducer positions 1008 a-1008 c a few times. FIG.16A, FIG. 16B, and FIG. 16C illustrate TCD sensor 1010 placement forinsonating the MCA 1012. FIG. 17 illustrates temporal window 1014landmarks and limits. Specifically, the anterior limit 1016 is near theorbital bone of the eye 1017. For patient safety, it is preferred not toimage near the orbital bone of the eye 1017. The superior limit 1018 isnot defined by any specific landmark. The inferior limit 1020 isidentified by the zygomatic arch (cheek bone). The posterior limit 1022is by the ear and provides a natural limit for the temporal window. FIG.18A and FIG. 18B illustrate example TCD locations 1024 as they vary fromperson to person, with dots 1026 representing the location of thetemporal window.

To locate the temporal window, a transducer is typically placed againstthe head. In the past, this step was typically assisted by an experthuman user. The user placed the transducer against the temple in theapproximate location of the window and kept manually reorienting thesensor until the signal was located. A semi-automated device may try toincrease signal strength at this point by reorienting the transducer,but with only two degrees of freedom, less than satisfactory results areachieved when attempting to fully automate signal discovery.

According to some embodiments, four, five, six, or even more of degreeof freedom (DOF) kinematic mechanisms are used that fully automate theevaluation of the temporal window quality and can rediscover thetemporal window even after complete loss of signal, as disclosed belowin the section entitled “G. Kinematics.”

In some embodiments, with the transducer seated, compliance is keptnormal to the surface high enough to keep the transducer seated, but lowenough so to be comfortable as the transducer moves in and out followingthe surface of the head. The X and Y axes can retain a higher servostiffness in order to maintain precision control of transducer location.Because the normal force of the transducer is determined by the Z axisstiffness, the sliding force encounter by the X and Y axes will belimited to a comfortable level. The transducer can now be directed toperform a search for the TCD window. If the orientation of thetransducer needs to be changed, the orientation stiffnesses can beincreased via software.

Registration:

As discussed in more detail below, in some embodiments, a computergenerates commands and directs the mechanism to translate and reorientthe transducer along the surface of the head until a candidate signal islocated. Once located, the transducer is then automatically reorientedto increase signal strength. Reducing the search time of the automatedsystem to discover the temporal window may be accomplished by a processof anatomical registration involving alignment of the mechanism andtransducer at a known anatomical feature, either manually orprogrammatically.

Programmatic Registration:

If done programmatically, this alignment may be accomplished with avisual window guide for the user to place an initial starting pointalong the zygomatic arch between ear and the eye. This anatomicalregistration technique is applicable to TCD, but can also be used withultrasound, fNIRS, and TCCS. In general the techniques and devicesdiscussed herein specifically described as using TCD can also beemployed in various embodiments using TCCS, other known ultrasonicenergy modalities, and fNIRS. Specifically, as shown in FIG. 19A, basedon existing literature, several different registration points, frontal F1028, anterior A 1030, medial M 1032, and posterior P 1034, may be usedto define a transtemporal search window. Insonation of frontal F 1028,anterior A 1030, medial M 1032, and posterior P 1034 normally occursboth at different x and y locations on the temporal window, as shown inFIG. 19A as well as with different rotational positions of the sensor,as shown in FIG. 19B. Once the transducer is placed at a registrationpoint, the robot is informed of which registration point is beingprobed. Different registration points could be used depending on whichartery is to be insonated. For example, the MCA, ACA, and PCA arteriesmay be identified using different registration points. FIG. 19C showsvarious locations that can be insonated, including the transtemporalwindow 196, the transorbital window 198, the submandibular window 200,and the suboccipital window 202. While registration points for thetranstemporal window 196 have been described, other registration points,for the transorbital window 198, the submandibular window 200, and thesuboccipital window 202 could also be applied. Once registration pointsare established, all coordinates are reported relative to theregistration points to impose a standard coordinate system across allsubjects. For example, in some embodiments, the coordinate (0, 0) wouldcorrespond to the posterior limit 1022 of FIG. 17, and the coordinate(1, 0) would correspond to the anterior limit 1016 of FIG. 17.Alternatively, if a scan of a specific subject has been conductedpreviously, the information already obtained for that subject may beused to conduct registration. As shown in FIG. 19D, a six degree offreedom robot arm 190, which can also be referred to as a redundantmanipulator, could be employed to move a transducer 20 to any convenientlocation on a subject. In other embodiments, the robot has fewer degreesof freedom such as five (x,y,z,pan,tilt) or is underactuated such thatone is controlled in part by a spring. As shown in FIG. 19E, the sixdegree of freedom robot arm 190 could be mounted with a portableworkstation 192 that includes a monitor 194. As shown in FIG. 19F thesix degree of freedom robot arm 190 could place the transducer 20 at thetranstemporal window 196. As shown in FIG. 19G the six degree of freedomrobot arm 190 could place the transducer 20 at the transorbital window198. As shown in FIG. 19H the six degree of freedom robot arm 190 couldplace the transducer 20 at the submandibular window 200. As shown inFIG. 19I the six degree of freedom robot arm 190 could place thetransducer 20 at the suboccipital window 202.

Automatic Signal Acquisition:

Referring to FIG. 20, in some embodiments, automatic signal acquisitionmay be accomplished automatically using a data-driven search algorithmto identify energy levels exceeding a specified or predefined threshold.The instructions specifying the algorithm may be provided in software,firmware, or other computer readable media. As used in thisspecification, any software, firmware, or other computer readableinformation mentioned, may be stored on non-transitory media, such as ahard disk drive, a flash disk drive, in ROM, or other non-transitorymedia. Specifically, in a system 1040 using a computer to direct thesearch process, in some embodiments, a stack-search is used. Astack-search allows for optimizing in a global-to-local search paradigm.The functional value that is being optimized is some measure T computedon sensor data, in some embodiments T could represent the energycomputed on an underlying TCD signal as acquired by a transducer.Function T, however, is not described by a known underlyingdistribution, but is instead a black box function with respect to sensorposition. Energy values cannot be inferred ahead of time in this type ofblack box search because the underlying signal distribution is unknown.In some embodiments with a 5 DOF robot and a TCD signal withcontrollable depth, T is computed by visiting some location positionp=(x, y, z, rx, ry, d) and computing T(x, y, z, rx, ry, d), where x, y,z are the translational positions of the sensor, rx, ry are therotational position of the sensor, and d is the sensor's sample depth.T(x, y, rx, ry, d) is sampled by moving the robot to position (x, y, rx,ry, d) and measuring signal and computing the energy at the position.Before discussing further aspects of the algorithm, some background willbe provided.

Energy Computation:

Energy computation is a joint function of the M-mode, the envelope, thespectrogram, and the depth, as well as any other information provided bythe TCD. A standard energy embodiment can be calculated as either of:

Energy(mmode,env,spec,depth)=α·mmode_eng(mmode)+β·env_eng(env)+y·spec_eng(spec)+δ·depth_eng(depth)  (Eq. 1)

Energy(mmode,env,spec,depth)=α·mmode_eng(mmode)×β·env_eng(env)×y·spec_eng(spec)×δ·depth_eng(depth)  (Eq. 2)

Examples of energy for TCD include the following.

Envelope:

For the envelope, in one embodiment the time-frequency structure can bedetermined via a discrete wavelet transform. Wavelet power is obtainedat narrow-band scales characteristic of TCD periodicity, e.g., heartrate, P2, and the like, and compared to broad-band power obtained overadjacent scales. Strongly periodic envelopes will have a greaterproportion of power at characteristic scales. Noisy envelopes are lesslikely to show strong concentration of power in any narrow-band becausewhite noise contributes power equally at all scales.

Autocorrelation is a mathematical tool for finding repeating patterns,such as the presence of a periodic signal obscured by noise, oridentifying the missing fundamental frequency in a signal implied by itsharmonic frequencies. In another embodiment, autocorrelation with ashifted waveform for periodic signals can be evaluated in the followingmanner, yielding another energy computation possibility. Given thatenv[t] is the signal at time t, the autocorrelation function at lag 1can be expressed as:

R _(env)(l)=\sum env(t)×env(t−1)   (Eq. 3)

R will have three strong peaks (besides near zero) and strong valleysbetween them, indicating a pulsatile waveform with 3 strong frequencies.

env_eng can also be embodied as the time-averaged envelope summed withthe time-averaged second derivative of the envelope, enforcingvelocities in a particular range, and a forced smoothness.

M-Mode:

In various embodiments, the width of the M-mode band may be used forcalculations. In some embodiments, the summed power in the M-mode may beused for calculations. In some embodiments, the M-mode energies can bemasked by a particular depth range if needed for a given vessel searchin TCD.

Spectrogram:

In various embodiments, the weighted average of the spectrogram signal,weighted by the particular bin number associated with each power valuemay be used. In some embodiments, the weighted average of thespectrogram signal, weighted by the inverse of the distance from theenvelope for each power value may be used. For example, this weightingcould be a one-side weighting, where for example all spectrogram datalying above the envelope is counted as zero towards the energy.

Search Optimization:

If a simple brute force snake search, as illustrated in FIG. 12 of, forexample, a 55 mm by 55 mm transtemporal window were conducted, using afive degree of freedom mechanism that moves along an X axis at 1 mmresolution, a Y axis at 1 mm resolution, a 30 degree by 30 degree X andY rotational dimensions (rx, ry) and a TCD depth of 75 mm, approximately200 million points would need to be searched. Such a search would take asignificant amount of time. In some embodiments, the search time can beoptimized using a data-driven search algorithm implemented on a roboticsystem searching across a pre-defined area, as discussed below.

Data Driven Searching:

Referring again to FIG. 20, in some embodiments, the system firstinitializes at the initialization step 1042. A database of seed points1044 may exist. In some embodiments, manual measurements from actualsubjects may comprise the database of seed points. Based on measurementsfrom made by technicians, x and y positions of transducer position forthe MCA can be used, and the data is clustered using a standardclustering algorithm such as k-means, and the cluster center points areused as seed points into the algorithm.

Referring again to FIG. 20, in some embodiments, the database of seedpoints 1044 is created by searching seed points via robotic scans of theselected window (e.g., temporal, orbital, sub occipital, submandibular)across a large number of subjects and storing energy computations forpoints in each window across the entire window. In some embodiments, thecomputerized robotic system employed has perfect memory, thus allowingfor recall of particular signals for a particular subject after thesignals have been found. For example, in some embodiments, ACA, MCA, PCAmonitoring positions for a particular subject are all stored in memoryand the operator can select one of them, commanding the robot to returnto that position and display the particular waveform. This ability torecall specific monitoring positions for a particular subjectfacilitates long term monitoring of a subject because monitoring can bedone quickly without needing to start a search from scratch.

Using this technique of generating a database of seed points, thousandsof data points can be aggregated across subjects. Layering the collecteddata across numerous subjects provides a probability distribution oflikely window seed points and search biases to speed up the search.Thus, in some embodiments, the search space may be limited by specifying(x_(i), y_(i)) Cartesian coordinates to seed a search at based on highprobabilistic chances that a temporal window is found at (x_(i), y_(i)).Additionally, in some embodiments, for a given point (x, y), thetransducer rotational orientation is limitless, but the data acquiredpreviously allows for a systematic bias for particular transducerorientations given a set translational point (x, y), greatly limitingthe search space. For example, in some embodiments, if the roboticsrotational range is ±15° in both pan and tilt, the search range canpotentially be limited at a given coordinate if a signal has only beenfound at the coordinate for a pan of 7-15° and a tilt of 3-10°. In someembodiments, seed points are chosen based on the race, gender, or age ofsubjects. A generate start point module 1046 then determines an initialstart point based on the artery to be scanned.

Push/Pop Search-Stack:

In some embodiments, a push/pop search-stack module 1048 is used toconduct the search. In some embodiments, this module is implemented insoftware on a computer with a central processing unit and associatedhardware to monitor information received from a transducer. In otherembodiments, this module can be implemented in other types of digitalelectronic circuitry, or in an ASIC, FPGA, or firmware, or hardware,including the structures disclosed in this specification and theirstructural equivalents, or in combinations of one or more of them. As isknown to those of skill in the art, pushing an element adds an elementto the top of a stack. Popping an element removes the top element of astack. The push/pop search-stack module 1048 contains a generate nextsearch module 1050, an execute search module 1052, a search stack 1054,and an evaluate search value module 1056. At the beginning of a search,no signal has yet been obtained upon which can be optimized.Accordingly, it is preferable to start with a broad, coarse search,which is just looking for a hint of a signal. In some embodiments, anexample of the initial search would be a coarse brute force snake searchacross the entire temporal region, or a coarse spiral/concentric circlescentered at the initial seed point.

Each subsequent search is a product of previous searches and theirresults. As points of interest with strong signals are located, searcheswill be refined or graduated in the areas of the strong signals. Thegenerate next search module 1050 generates an initial search S₀ 1056,which is a very coarse search. In some embodiments, if and when a pointof interest is located during the search, a new, finer search S₁ 1058 isidentified and pushed onto a search stack 1054. For example, if a coarsespiral search is being conducted, and a point of interest is discovered,then a finer spiral search could be pushed onto the state stack. If thefine spiral search finds another point of even higher interest, then aneven more refined search would be pushed onto the state stack and thusconducted. If search S₁ 1058 generates useful additional points ofinterest, an even finer search S₂ 1060 is generated and pushed on thesearch stack 1054, and so on. In some embodiments, the “point ofinterest” energy threshold is increased or made more strict as thesearches become more refined. In general, if a search S_(n) does notgenerate any useful additional points of interest, search S_(n) ispopped off the search stack 1054 and that search state returns to thestate it was at during search S_(n-1) and continues using thepotentially less strict energy threshold as was specified for S_(n-1).

After each search is executed by the execute search module 1052, anevaluation of the returned value of the execute search module 1052 ismade by evaluate search value module 1056. If the returned value of theexecute search module 1052 does not satisfy a finishing criteria, then anew search is generated by the generate next search module 1050, and thecycle continues. If the returned value of the execute search module 1052does satisfy a finishing criteria and the signal obtained issufficiently useful, the evaluate search value module 1056 exits and thereturned value of the execute search module 1052 is added to a set ofuseful points 1062 and the search stack 1054 is cleared. Next, the endof search decision module 1064 determines whether sufficient number ofuseful points have been identified. If a sufficient number of usefulpoints have not been identified, the generate start point module 1046generates a new search and the cycle continues using the next seedpoint. In another embodiment, all search points visited and theircorresponding energies are stored in a sorted list. This list can befiltered to keep only the best energies given some spatial resolutionconstraints. The top of the list has the highest energy points and theserepresent the useful points for the next part of the algorithm.

If a sufficient number of useful points have been identified, the searchalgorithm terminates. At this step, the select point module 1066 may askan operator, or may decide automatically, whether any point located inthe prior searches is of interest. Once a point of interest is selected,the track module 1068 directs a robotic mechanism to move to the pointof interest and analyze the signal. In some embodiments, the point ofinterest may be selected based on computed energy value (e.g. thehighest energy is assumed to be the best point) or based on metadatasuch as a point label (e.g. MCA, ACA, PCA for TCD). In some embodiments,the system 1040 will then monitor that point, continuously tracking theenergy at that point. In some embodiments, if the energy degrades by acertain percentage (e.g., 10% degradation), the system 1040 will thenconduct a local optimization near that point, using a track module 1068to re-acquire the ideal signal. This re-acquiring of the signal issignificant because patients often move or talk, causing the system 1040to lose the signal. In some embodiments, at any point, the operator mayselect a different point of interest to examine.

Referring to FIG. 23, in some embodiments of a stack-search algorithm, asystem 1080 using a computer programmed with software to direct thestack-search process, has an initialization module 1082 whichinitializes variables. The system 1080 then registers anatomicalreference points in the register anatomical reference points module1084. A database of seed points 1086 may exist, which contains a set ofseed points ρ 1085, which may be used by the search seed points module1088 to determine which seed points to search or the search seed pointsmodule 1088 may use information received from the register anatomicalreference points module 1084. The database of seed points 1086 may bestored on non-transitory computer readable media. An initial searchpoint module 1090 then determines an initial seed point “p” to searchand provides that point to the initialize state-stack search module1092. The initialize state-stack search module 1092 creates a searchstack 1094 based on seed points p.

In some embodiments, a get search type module 1096 determines a searchby popping the top element off the search stack 1094 and provides thesearch type S to the generate search points module 1098. The generatesearch points module 1098 generates a set of points to search Ω based onthe search type S. If no additional points exist in the set of points tosearch Ω, then the top element of the search stack 1094 is popped off bythe stack pop module 1100 and provided to get search type module 1096and another search type S is retrieved from the generate search pointsmodule 1098.

In some embodiments, if points exist in the set of points to search Ω,the point identification module 1102 identifies a point p to search bypopping it off the top of the set of points to search Ω and directs therobotic mechanism to go to point p. The analyze energy module 1104 thenanalyzes the energy e received from the energy directed at point p. Ifthe energy e is below a specified energy threshold, possibly indicatingthat a vessel has not been located, in some embodiments a search timeoutdecision is implemented via timeout module 1106. Search timeouts havespecial utility in time-critical situations, such as a stroke diagnosisin which emergency medical intervention may be required. In someembodiments the duration of the search timeout is a predefined intervalof time used for every search. In some embodiments, the duration of thesearch timeout is dynamic that changes. In some embodiments the durationof the search timeout updates every time the finest search S_(N) isconducted, and the duration of the search timeout may either beincreased or decreased, depending on the desired outcome, for exampleincreasing search thoroughness, or increasing search speed. In someembodiments the duration of the search timeout may be based, in part, onthe amount of time spent searching.

In some embodiments, if no search timeout is taken and there are morepoints to search in the set of points to search Ω, the next point p isidentified by the point identification module 1102 and the cyclecontinues. Alternatively, if there are not more points to search, theget search type module 1096 determines a search by popping the topelement off the search stack 1094 and the cycle continues.

In some embodiments, if a search timeout is taken then the evaluate seedpoint set module 1116 evaluates whether the set of seed points ρ 1085constitutes the empty set Ø. If the set of seed points ρ 1085 does notconstitute the empty set Ø, then initial search point module 1090generates a new initial point to search and the cycle continues.Alternatively if the set of seed points ρ 1085 does constitute the emptyset Ø, then no more seed points exist and the set of candidate points θ1118 is returned. Then in the user selection step 1120, the user thenselects a point p*, and its corresponding energy e* from θ 1118 and therobot is directed to go to point p*. Track mode is then entered, asdiscussed above. In the compute energy module 1122, the systemcontinuously computes the energy e at p*. The compare energy module 1124determines whether e falls below some fraction σ of the original energye*. If compare energy module 1124 determines that e has fallen belowsome fraction σ of the original energy e* then the optimization module1126, re-optimizes, computing a new point p* and its corresponding e*.

Referring again to the analyze energy module 1104, if the energy e isabove a specified energy threshold, then the stop determination module1108 makes a determination as to whether to stop the search. In someembodiments, the determination to stop the search may be based on somecombination of the amount of energy e received, the search type S, orthe time spent searching.

In some embodiments, if the stop determination module 1108 determinesthat the search should not stop, then the graduate search module 1110identifies the next search to conduct and pushes onto the search stack1094 a finer search.

In some embodiments a maximum search iteration module 1112 determineswhether the maximum number of searches allowable has been conducted.This maximum search iteration module 1112 provides a method of limitingthe time spent searching. In some embodiments, the maximum searchiteration module 1112 may base the decision regarding whether themaximum number of searches allowable has been conducted on somecombination of the total time spent searching, the total number ofiterations of searching conducted, or the total number of searchesconducted at the finest search time S_(N).

In some embodiments, if the maximum number of iterations has not beenreached then a threshold update module 1114 may perform a dynamicthreshold update for the minimum acceptable energy level. In someembodiments, it is important to update this threshold because there aresignificant anatomical differences among subjects. Some subjects havevery poor signals and the embodiment may be required to obtain the bestsignal possible in a predefined amount of time, so thresholds areinitially set low. Other subjects have very strong signals, and usingthe same thresholds on these subjects as were used with the poor signalsubjects will result in poor final signals compared to what they couldultimately be yielded if higher thresholds were imposed. In someembodiments, dynamic thresholds will be updated after the completion ofeach successful search, and the threshold will be updated to increasethe difficulty of locking onto a signal during the next iteration of thesearch cycle.

TCD Search and Signal Processing Algorithm:

The problem of an automated TCD system with a path planning and signalprocessing algorithm that searches for a TCD signal while directing thegeneral motion of the transducer, can be separated from the robotcontrol problem of being able to automatically follow a contouredsurface (as would be found on a head). The rationale for this separationis that the detection algorithm is a signal processing andmotion-planning problem that encapsulates some of the innovation. Theinteraction is with a small area of the head that can be simplified to anominally 2D surface, which puts the focus of this objective on theplanning and signal processing algorithm development. Having atransducer follow a contoured surface while maintaining a normal angleis a technical task that extends the applicability of the systemeventually to human subjects, but is not dependent on TCD signalinterpretation. In some embodiments, the system can deploy an ultrasoundtransducer against a contoured 2-d surface, and slide the transducer atconstant velocity while maintaining a constant normal force between 2and 10 Newtons.

Search Types:

In various embodiments of the search system, many different types ofsearches may be employed. Specific search types are discussed below.

Grid Search—Cartesian:

The simplest window and signal discovery is a brute force approach. Insome embodiments, a five degree of freedom robot is used. Given abounded search area, the search algorithm will direct the robot to placethe transducer onto the flow phantom interface and then move it througha Cartesian grid of discrete points in a segmented step size, stoppingto check the velocity envelope signal at each point. As discussed inmore detail below, in some embodiments, the TCD transducer will alsoneed to be set to a grid of sample depths to find the maximum signal atthat point. Once the grid is complete, the location of the maximumsignal can be determined and the transducer repositioned to thatlocation, as illustrated in FIGS. 12 and 13. In some embodiments, thedimensions are X, Y, rotation in the X axis, rotation in the Y axis, anddepth of insonation, or TCD depth, which step sizes are represented bydx, dy, drx, dry, ddepth, respectively. As noted above, using arelatively small step size such as 1 mm, a snake/grid search may beinefficient and time consuming. Using a coarser step size, which greatlyprunes the number of searches conducted, such a snake/grid search may beappropriate for imprecise studies, such as window mapping.

This algorithm also sets a baseline performance metric to compare otheralgorithms to. For one version of the algorithm, the string phantom isset to a constant velocity, simplifying the signal detection to checkingthe magnitude of the velocity envelope. Once constant velocity can bedetected, the complexity of the problem will be increased by setting thestring phantom to mimic pulsatile flow. In some embodiments, what isused is perhaps simplest pulse detection algorithm, which employs a bandpass filter centered at the beat frequency to determine presence andmagnitude of the TCD signal.

In order to reduce the time for the optimal TCD velocity signal to befound, or a TCD velocity signal exceeding a predefined threshold, thetransducer will be constantly moving while the search algorithm checksthe sensor data, as illustrated in FIGS. 12 and 13. Complicating thistask is that transducer motion can couple into the output signalyielding false positives. In some embodiments, implementing thisalgorithm involves characterizing the motion coupling noise into thetransducer output to determine the maximum scan speeds and signalfilters to ameliorate the noise. For example, during the constantvelocity string phantom case, noisy signals are sometimes generated, anda low pass filter may be used to decouple the noise due to transducermotion sliding artifacts from the DC velocity signal coming from thestring phantom. In some embodiments, for pulsatile motion a band bassfilter or other probabilistic detection method, such as a Bayesianfilter may be used.

Grid Search—Cartesian and Orientation:

The magnitude of the velocity signal is proportional to the Dopplerangle as a function of the cosine, v_(z)=∥{right arrow over (v)}∥ cosθ_(D). changing the orientation of the transducer can affect the qualityof the signal. Changing the transducer angle also allows for searching avolume for the target vasculature at one location instead of justemitting a line of projected ultrasound acoustical energy, as shown inFIG. 14. This algorithm repeats the Cartesian grid search adding a gridof orientation angles of the transducer (pan and tilt) to sweep out asearch volume. By triangulating on the maximum signal location, thissearch picks an optimal transducer orientation and position that maydiffer from the Cartesian only grid search. Overlapping search volumescan be created by repositioning the transducer a few times.

Simulated Annealing:

Another search type used in some embodiments is simulated annealing.Simulated annealing is a search method known to those of skill in theart. Simulated annealing provides a method of determining a likely good,but not necessarily optimal, solution to an optimization problem. Ingeneral, and simplified, terms, simulated annealing searches for thebest solution by generating an initial solution at random and thenexplores the area nearby randomly to generate a new solution. If the newsolution is better than the current solution, the new solution replacesthe current solution, and it is saved as the base of the next iteration.Alternatively, if the solution in the neighboring vicinity is worse, thealgorithm calculates an acceptance probability and compares it to arandom number. If the acceptance probability is higher than the randomnumber, the new solution replaces the current solution, it is saved asthe base of the next iteration. Otherwise, the new solution does notreplace the current solution.

Spiral Search:

Another search type used in some embodiments is a spiral search. Aspiral search originates at a seed point. The search can be coarse orfine, depending on the application. Instead of moving along an X axisuntil an end is reached and then adjusting the Y direction as in theCartesian search, a spiral search adjusts angular separationsimultaneously in the X and Y directions to make the transducer spiraloutward from the initial seed point. A coarse spiral search expands morequickly than a fine spiral search.

Concentric Search:

Another search type used in some embodiments is a concentric search. Aconcentric search starts at a seed point as the initial position andthen typically adjusts either the X or Y direction to come to a newposition defining a radius from the initial position. From the newposition, the search adjusts both the X and Y axes to search in acircle. Once the starting point of the circle is returned to, anotherradial adjustment is made and a search of the new circle is conducted.

Hill Climb:

Another search type used in some embodiments is the hill climb. The hillclimb technique is another technique known to those of skill in the artfor efficiently finding local optima that can be used in variousembodiments. In general, and simplified, terms, a hill climb techniquestarts at a seed point as the initial position. The initial position isanalogized as the base of a hill. The technique then repeatedly improvesthe solution finding a better signal, which is analogized to walking upa hill, until some condition is maximized and a satisfactory signal isfound.

Contra-Lateral Search:

Some technicians have reported that a signal acquired on the ipsilateralis often reflected, position-wise, in the contra-lateral side. In someembodiments, this domain knowledge is exploited in embodiments of thesearch algorithm. Specifically, in some embodiments in which a bilateralscan is conducted, if a signal is detected, for example, on thecontra-lateral side, the position and signal strength information willbe provided to the processor conducting a scan on the ipsa-lateral side,and vice versa. Continuing with the example, the processor for theipsa-lateral side then assess the broadcasted signal strength and makesa determination of whether a search should be started centered at thesymmetric point provided by the contra-lateral side. In someembodiments, this search can either be done by immediately abandoningthe current search and moving to the point, or adding the symmetricpoint to the list of seed points for the algorithm.

D. Vessel Signal Optimization

In some embodiments, once the system has placed the transducer on theskin (See Automatic Transducer Placement) and identified a candidatewindow (See Automatic Window Discovery), the embodiments then identifythe optimal signal, as discussed above. In currently existing manualsystems, this optimization is sometimes being done by the technician“optimizing” the transducer angle, sound, depth, waveform fit, spectrum.

Overview:

In some embodiments, signal optimization is important. For TCD, thestrength of the echoed blood flow velocity signal strength decreases asa cosine function of the angle of incidence between the ultrasound beamand the blood flow. For purposes of a machine learning algorithm, a lossof signal can disrupt the final diagnosis. Many external factors cancause signal weakening: TCD transducer slippage relative to the head,mechanical creep in TCD head mounted fixtures, patient motion, and thelike. Even just achieving and maintaining the maximum signal isdifficult for an expert user. Fundamentally, all of these problemscenter on minimizing the angle of incidence of the ultrasound beam andthe blood flow.

In some embodiments, controlling for this angle incidence requiresplacing the sample beam location of the TCD sensor in Cartesian space,(x,y,z), onto the arterial structural, and then minimizing theorientation error (angle of incidence) between the direction of the beamand the direction of the blood flow. Setting the orientation of thesample location requires two degrees of freedom—pan, tilt. In total aminimum of five degrees of freedom must be used to kinematicallyguarantee at least one solution where the orientation error is zero (oras close to zero as possible has defined by the limits of TCD windowanatomy and vessel orientation). Some currently available TCD productsautomatically control for only the two orientation degrees of freedom.

Some embodiments provide a five DOF mechanism that when coupled with aTCD sensor, controls the depth setting of the TCD. This mechanismcreates a virtual link to the ultrasound sample location within thebrain and in total a six DOF kinematic chain. In some embodiments aredundant manipulator also exists that can adjust itself with smallmotions while maintaining maximum signal strength. In some embodiments,a sample volume is placed at a three dimensional location within thevessel and the orientation of the sample is adjusted to align itselfwith the vessel blood flow in order to minimize the angle of incidence,which increases signal strength.

Limitations of Current Two DOF Systems:

It is important to note the limitations of two degree of freedomsystems. Currently available TCD system with two automatic DOFs andcontrol of the TCD depth as a third DOF, can place a sample volumewithin the brain at a Cartesian location (x,y,z). With only three totaldegrees of freedom, the orientation of the sample cannot be specified.Therefore, the angle of incidence to the blood flow cannot be set sothere is no guarantee of the signal strength. The angle can only beadjusted by the user manually moving the transducer. Signal acquisitionand optimization remains a manual process, with the fundamental geometryunlikely to be understood by the user.

Optimizing Signal Strength:

With a five DOF mechanism, and using the depth setting of the TCDtransducer, the sample volume Cartesian location (x,y,z) and orientation(pan,tilt) can be specified. For the device, the following describes arelationship between the input mechanism and TCD settings, Q={q₁, q₂,q₃, q₄, q₅, TCD_(depth)} to the sample volume location and orientationX={x,y,z,pan,tilt}, which is called the forward kinematics

X=fwd_kin(Q)

Similarly an inverse relationship called the inverse kinematics canderive mechanism settings Q from a desired sample location andorientation, X.

Q=inv_kin(X)

For a given Cartesian location within the brain (x,y,z), pan and tiltcan be adjusted to maximize the signal strength by minimizing a costfunction based on orientation error.

Use of a Redundant Degree of Freedom:

When the mechanism is able to press the transducer into the head becauseof skin and tissues compliance, there is a brief area before the zmotion of the transducer into the head becomes constrained where thereare six controllable degrees of freedom. In this region, there is oneextra degree of freedom which creates a redundant kinematic chain. Themechanism can now reconfigure itself, from Q₁ to Q₂ while maintainingthe sample position and orientation X via the relationship

Δq=J ^(†)

+(I−J ^(†) J)φ

where Δq is the change in mechanism configuration, J is the Jacobianwhich relates differential joint motion Q to differential task spacemotion X, J^(†) is the pseudo inverse of the Jacobian, J^(†)é is theterm that corrects for sample position error, and (I−J^(†)J)φ is thenull space that maps a desired change in Q into a Δq that does notaffect X.

This extra degree of freedom allows for multiple approaches or mechanismconfigurations to signal discovery and maintenance. It also allows forrepositioning of the mechanism while maintaining signal lock.

It is important to note that the Z action of the device must not becoincident with depth action of the TCD, or a degree of freedom will belost. This approach only works while the mechanism can move thetransducer within the compliance of skin.

Gradient Descent and Optimizing Signal Strength after Lock:

Some embodiments are not limited to straight line, constant velocitymoves. As the transducer motion commands can be updated in real time ata rate of at least 125 Hz, other non-linear search paths can be created.By taking advantage of being able to change the orientation of thetransducer and the depth information from M-Mode, a gradient descentalgorithm can be implemented that maximizes a TCD velocity signal. Oncethe candidate location is found, the signal strength at the currenttransducer location can be optimized by reducing the Doppler angle. Thisoptimization will result in more rapid detection of a the TCD signal.The approach for signal strength optimization is as follows:

Optimization of Blood Velocity Signal from TCD Measurements Using aRobotic Device:

When measuring the blood velocity using a TCD sensor, maximizing thesignal strength is important for analysis. Signal strength is dependenton the Doppler angle, θ_(D), between the blood velocity vector, {rightarrow over (v)}, and the orientation of the normal to the TCD sensorsurface or emission axis, {right arrow over (z)}. The measured velocityalong the TCD emission axis, v_(z), varies as function of the cosine ofthe Doppler angle.

v _(z) =∥{right arrow over (v)}∥ cos θ_(D)   (Eq. 4)

The optimization of this relationship is to simply minimize the Dopplerangle.

Approach:

In some embodiments, a robotic device holds the TCD sensor whilecollecting data from a section of the cerebral artery. The position andorientation of the TCD sensor is known from the robot kinematics.Because the depth setting of the TCD is also known, the position of thesample within the brain can be thought as the final step of thekinematic chain of the robot. This sample has the same orientation asthe TCD sensor. The measured velocity should be a function of theDoppler angle between the sample normal axis {right arrow over (z)} andthe blood velocity vector, {right arrow over (v)} as described throughEq. 4. In some embodiments, the robotic device can reorient the TCDsample while maintaining its position. The TCD sensor itself will needto change position and orientation, but the location of the sample inthe brain will remain constant. At each reorientation, the Doppler anglechanges and the new velocity is measured. Given a collection of enoughsample orientations and their respective velocity measurements, and therelationship described in Eq. 4, allows for solving for {right arrowover (v)} which will determine both the optimal orientation to collectTCD data, and predicts the maximum blood flow.

Analytic Solution:

Assume that the origin reference coordinate frame is the beginning ofthe robot kinematic chain. The orientation of the sensor can bedescribed by a coordinate frame attached to the surface of the TCDtransducer with the Z axis normal to the surface. This coordinate framecan be derived from the robot's forward kinematics and is described by arotation matrix. The columns of a rotation matrix are the orthogonalunit axes of frame n written in the coordinates of frame 0.

_(n) ^(o) R=[{right arrow over (X)}{right arrow over (Y)}{right arrowover (Z)}]   (Eq. 5)

If this coordinate frame is translated a distance d equivalent to thesample depth setting of the TCD sensor, it will now lie coincident withthe blood flow velocity vector, {right arrow over (v)}, that is beingmeasured. The orientation of the axis of emission of the TCD sensor isdescribed by the z-axis of the rotation matrix in Eq. 5, {right arrowover (Z)}, which falls out of the kinematics. The angle between the twovectors is the Doppler angle. The angle between the two vectors can berelated with the vector dot product

{right arrow over (Z)}·{right arrow over (v)}=∥{right arrow over(Z)}∥∥{right arrow over (v)}∥ cos θ_(D)   (Eq. 6)

The magnitude of {right arrow over (Z)} is already normalized. Bynormalizing {right arrow over (v)} Eq. 6 reduces to

{right arrow over (Z)}·{right arrow over (v)} _(norm)=cos θ_(D)   (Eq.7)

For each measurement made at a set position {right arrow over (P)} witha different orientation _(n) ^(o)R, a measured velocity _(n)v_(z), isgenerated with a z-axis orientation, _(n){right arrow over (Z)} wherethe measurement index is n=1, 2, 3 . . . . The analytic solution can bederived by substituting Eq. 7 into Eq. 5 and making three measurementsto generate three equations.

_(n) v _(z) =∥{right arrow over (v)}∥(_(n) z ₁ v _(norm,1)+_(n) z ₂ v_(norm,2)+_(n) z ₃ v _(norm,3))   (Eq. 8)

Making a substitution of variables c₁=∥{right arrow over (v)}∥v_(norm,1)

₁ v _(z)=₁ z ₂ c ₂+₁ z ₃ c ₃

₂ v _(z)=₂ z ₁=₂ z ₂ c ₂+₂ z ₃ c ₃

₃ v _(z)=₃ z ₁=₃ z ₂ c ₂+₃ z ₃ c _(3 (Eq.) 9)

With three equations and three unknowns this can be solved using thefamiliar 3×3 matrix inverse solution

$\begin{matrix}{\begin{matrix}{a_{11}} & a_{12} & {{a_{13}} - 1} \\{a_{21}} & a_{22} & {a_{23}} \\{a_{31}} & a_{32} & {a_{33}}\end{matrix} = {{1/{DET}^{*}}\begin{matrix}{{{a_{33}a_{22}} - {a_{32}a_{23}}}} & {- \left( {{a_{33}a_{2}} - {a_{32}a_{13}}} \right)} & {{{a_{23}a_{12}} - {a_{22}a_{13}}}} \\{{- \left( {{a_{33}a_{21}} - {a_{31}a_{23}}} \right)}} & {{a_{31}a_{11}} - {a_{31}a_{13}}} & {{- \left( {{a_{23}a_{11}} - {a_{21}a_{13}}} \right)}} \\{{{a_{32}a_{21}} - {a_{31}a_{22}}}} & {- \left( {{a_{32}a_{11}} - {a_{31}a_{12}}} \right)} & {{{a_{22}a_{11}} - {a_{21}a_{12}}}}\end{matrix}}} & \left( {{Eq}.\; 10} \right)\end{matrix}$with DET=a ₁₁(a ₃₃ a ₂₂ −a ₃₂ a ₂₃)−a ₂₁(a ₃₃ a ₁₂ −a ₃₂ a ₁₃)+a ₃₁(a ₂₃a ₁₂ −a ₂₂ a ₁₃)   (Eq. 11)

Once the coefficients of Eq. 9 are solved, the magnitude of the bloodflow velocity can be computed from the vector coefficients.

∥{right arrow over (v)}∥=√{square root over (c ₁ ² +c ₂ ² +c ₂ ³)}  (Eq. 12)

This last result can be used to help verify that when the orientationwith the predicted max velocity is moved to, that it is indeed achieved.

Pan and Tilt Angles:

Analytic solution—If it is desired to describe the orientation of theblood flow in terms of pan and tilt angles, the pan and tilt angles canbe derived from the z-axis of the X-Y-Z fixed angle rotation matrix

$\begin{matrix}{{{{}_{}^{}{}_{}^{}}\left( {\gamma,\beta,\alpha} \right)} = \begin{bmatrix}\ldots & \ldots & {{c\; \alpha \; s\; \beta} + {s\; \alpha \; s\; \gamma}} \\\ldots & \ldots & {{s\; \alpha \; s\; \beta \; c\; \gamma} - {c\; \alpha \; s\; \gamma}} \\\ldots & \ldots & {c\; \beta \; c\; \gamma}\end{bmatrix}} & \left( {{Eq}.\; 13} \right)\end{matrix}$

by setting the yaw angle, γ to 0, and setting the coefficients c₁, c₂,c₃ equal to the third column of Eq. 13.

Numerical Solution:

If more than three samples are used, a numerical solution can be foundby extending the equations of (6) with the extra samples₁v_(z)=₁z₁c₁+₁z₂c₂+₁z₃c₃

$\begin{matrix}\begin{matrix}{{{}_{}^{}{}_{}^{}} = {{{{}_{}^{}{}_{}^{}}c_{1}} + {{{}_{}^{}{}_{}^{}}c_{2}} + {{{}_{}^{}{}_{}^{}}c_{3}}}} \\{{{}_{}^{}{}_{}^{}} = {{{{}_{}^{}{}_{}^{}}c_{1}} + {{{}_{}^{}{}_{}^{}}c_{2}} + {{{}_{}^{}{}_{}^{}}c_{3}}}} \\\ldots \\{{{}_{}^{}{}_{}^{}} = {{{{}_{}^{}{}_{}^{}}c_{1}} + {{{}_{}^{}{}_{}^{}}c_{2}} + {{{}_{}^{}{}_{}^{}}c_{3}}}}\end{matrix} & \left( {{Eq}.\; 14} \right)\end{matrix}$

and then by using a generalized inverse to solve for the coefficientsc₁, c₂, c₃

{right arrow over (c)}=Z ^(†) V   (Eq. 15)

Dynamic Dwell Time:

Some prior art two DOF systems dwell for a predefined period of time ateach position where the system attempts to locate a signal. In someembodiments, employing a dynamic dwell time and a stability signalanalysis can increase search speed significantly. In some embodiments,signal energy is computed after waiting at position for a predeterminedwait period of time to eliminate signal/noise transients. In someembodiments, for each position, the predetermined wait period iscomputed dynamically based on a signal stabilization analysis. In someembodiments, it is preferable to use M-mode data for the signal analysisinstead of pulsatile signal information, such as envelope and spectralinformation. Pulsatile signals are constantly changing and a mean signalanalysis could require at least 1 second of data. M-mode data is moreconsistent versus time because it is less sensitive to depth, and otherpositional parameters.

Rather than spending 200-300 ms at each position, some embodiments mayspend as little as 10 ms at a location when it is determined through adynamic dwell time analysis that no usable signal is present. In someembodiments, only a minimal amount of time is needed to be spent at alocation if the M-mode signal is near zero. In some embodiments,spending a minimal amount of time at a location significantly speeds upthe searching process because many positional data acquisitions onlyacquire noise level data.

E. Vascular Mapping

Vascular mapping may follow the signal to be optimized at several pointswithin the Circle of Willis. Therefore, the mapping feature may beperformed in connection with the following features: AutomaticTransducer Placement, Automatic TCD Window Discovery, and SignalOptimization.

Overview:

Traditionally, transcranial Doppler (TCD) ultrasound has been used forthe assessment of cerebral blood flow velocity (CBFV) at a discretepoint (depth) within the Circle of Willis with limited additionalinformation. Some embodiments provide a method to combine discretepoints into a “map” of the cerebral vasculature using an automated 6 DOFmechanism combined with an analytic approach for combining theultrasound data. This rendering of the dynamics of the vasculatureprovides clinicians a more complete view of the vasculature allowing forbetter diagnosis, triage, and monitoring of a number of neurologicconditions including stroke (hemorrhagic or ischemic), traumatic braininjury, migraine, dementia, and others. Some embodiments include severalsubsections including vessel identification, robotic kinematics, use ofanatomical context, and influence of bilateral monitoring

FIGS. 22-24 correspond to features of Vascular Mapping. The simplestform of TCD is a single-gate pulsed Doppler ultrasound. In this setting,velocity information is obtained from a single depth, as shown in FIG.22. FIG. 22 illustrates a CBFV spectrum 2400. For each CBFV pulsetraditional TCD calculated the systolic velocity 2402, diastolicvelocity 2404, and mean velocity 2406. Additionally, there is a velocityenvelope 2408 (peak velocity throughout the cardiac cycle), and thevelocity spectrum 2410. Additionally, multiple gates (depths) can beinsonated allowing for the collection of different velocity spectrum atdifferent depths within the cerebral vasculature.

A relatively recent development known as power M-mode Doppler samplesthe power at a large number of depths providing power and directioninformation, as shown in FIG. 23A. The spectral display of FIG. 23A iscalculated based on the depth represented by line 2500 in FIG. 23A.Although multi-gate and M-mode allow for a more complete “image” of thevasculature, limitations in information extraction/integration, uservariability, and single transducer monitoring prevent a usable vascularmap.

Information Extraction/Integration:

Despite reporting of the overall velocity spectrum shown in FIG. 24, insome existing systems, this information is not utilized to assessoptimal signal within a given vessel. Signal optimization is essentialfor accurate identification and visualization of the cerebralvasculature. M-Mode is an ultrasound presentation of temporal changes inechoes in which the depth of echo-producing interfaces is displayedalong one axis with time (T) along the second axis; motion (M) of theinterfaces toward and away from the transducer is displayed. M-Moderepresentations are based on power and mean velocity at a specificdepth, and therefore disregard the velocity spectrum. Integration of thevelocity spectrum is described below.

Manipulation of TCD Parameters:

In some embodiments, various TCD parameters can be manipulated,including signal gain, pulse repetition frequency (PRF), the samplevolume or length, and filtering the TCD signal to reduce noise.

In some embodiments, the depth of the sample volume is also manipulated.Specifically, a sample may be dynamically selected at specifiedintervals, and in some embodiments the specified intervals may rangefrom 0.01 s to 1 s. In some embodiments, the depth of the sample volumemay be guessed and checked for a given search position. For example, insome embodiments, such as a search for the MCA, the depth may be checkedat approximately 45 mm to 65 mm.

In some embodiments, the depth can be automatically computed. Forexample, in some embodiments the appropriate depth may be calculated bydetermining the maximum power at a depth as provided by M-modeinformation.

User Variability:

Despite the several measurement methods described above, traditional TCDsuffers from significant user variability. Manual or semi-automated (TwoDOF) systems do not provide a reliable signal and therefore areinadequate for complete insonation of the Circle of Willis.

Anatomical Feature Walking:

Limitations of current manual TCD technology and user variability makeit impossible or nearly impossible to construct a map of the path of ablood vessel. In some embodiments, using the robotic techniquesdescribed herein, including information concerning TCD signal strength,depth, and position, the robotic system can follow the path a bloodvessel takes walking through the path at various depths within the bodyof a subject.

Signal Classification Based on Waveform Analysis:

Identification of a particular vessel can be achieved by comparing thedepth, velocity, angle, and/or waveform morphology with those from asample population or within the individual's currently or previouslycollected waveform information.

In one embodiment, the waveform of an individual is compared to adictionary of labeled waveforms contained in a validated dictionary. Thecomparison can be done using a standard distance metric such as theL2-norm or the correlation distance. A subspace decomposition in asupervised, unsupervised, or semi-supervised way can also be used aloneor in conjunction with other distance methods.

In another embodiment, the waveform of the MCA captured below 50 mm isrecorded initially. Using the depth and velocity information theidentity of the MCA can be assumed. This waveform is used as the anchorvessel. Other vessels can then be insonated and recorded. The identityof these subsequent vessels can be determined using their physicallocation relevant to the anchor vessel. Ensuring their identity relativeto each other can be accomplished by a complete pairwise distancecomparison. Additionally, a subspace decomposition of the collectedwaveforms can be used to ensure adequate separation of the projectedwaveforms. This decomposition can be done after the collection of eachvessel or after all of them have been collected.

Bilateral Monitoring:

Although some prior TCD systems provided bilateral-monitoringcapabilities, those systems are independent of one another. In someembodiments, integration of the two probes provides verification ofoptimal velocity and decreased calculation duration.

FIG. 23A: Example of power M-mode. The power M-mode Doppler image 2502in FIG. 23A resides above the spectrogram image 2504 of FIG. 23A, sothat they share the same horizontal time axis. The power M-mode Dopplerimage 2502 shows depth from the transducer on the vertical axis, time onthe horizontal axis, and power of the Doppler shift signal at specificdepths as intensity. Simultaneously, the direction of blood flow isderived from the positive or negative mean value of the Doppler shiftsignal at the particular depth. As each new line in the spectrogram iscalculated and displayed, a corresponding power M-mode Doppler imageline is displayed concurrently in the PMD image directly above. Thehorizontal line 2500 in the PMD display in FIG. 23A indicates the gatedepth associated with the spectrogram in FIG. 23A. Also shown in FIG.23A is demonstration of beam alignment with the right middle cerebralartery 2506, right anterior cerebral artery 2508, and the left anteriorcerebral artery 2510. A schematic of the anatomy 2512 from which the PMDimage is derived is drawn in FIG. 23B, showing right middle cerebralartery 2506, right anterior cerebral artery 2508, and the left anteriorcerebral artery 2510 using a transducer 20, and ultrasound beam axis2514.

Cerebral Blood Flow Velocity:

As shown in FIG. 24, a major conducting vessel 2602 of the Circle ofWillis is commonly the Middle Cerebral Artery (MCA); however, it canrepresent any vessel. A cross section 2604 of an artery, with threeprojected samples volumes (TCD) 2606, 2608, 2610 is shown in FIG. 24.Optimal sample volume 2610, captures the true peak CBFV. Intermediatevelocity 2608 and, CBFV is lower because of partial voluming. Worksample volume 2610 placement is also shown.

5 or 6 DOF Mechanism—Information Extraction/Integration:

Some embodiments address the limitation of signal optimization throughintegration of fundamental elements of TCD. Manual insonation of theoptimal CBFV signal requires integration of several elements includingtransducer orientation, spectrum recognition, vessel identification, anddepth. These elements are developed through experience and unfortunatelylead to variability between users.

Orientation of the Transducer:

Over time, an expert user gains the ability to visualize the Circle ofWillis structure. The orientation of the transducer in X-Y and Θ-Φ spaceis not used. Combined with the depth information embodiments canidentify and record a sample volume in 3D space. Orientation and depthallows for more accurate vessel identification and mapping. Whencombined with bilateral monitoring some embodiments introduce a level ofverification as well.

Spectral Information:

As described, traditional analysis of CBFV is limited to the mostprominent features, systolic, diastolic, mean velocities, andPulsatility Index, as shown in FIG. 24. This analysis has been clinicalpractice for over 30 years and current machines are unable to capturethe full potential of the signal. In such analysis, importantinformation about the pulsatile CBFV waveform is lost.

By using a 5 DOF mechanism and a redundant depth DOF from the TCD(virtual six DOF kinematics), some embodiments manage position andorientation of the sample volume to maximize signal. By followingmaximized signal along normal flow velocity direction, some embodimentstrack along vascular structure—not grid scanning of entire head. Thisapproach is useful in signal acquisition and total vascular mapping.

Using multidepth information the software communicates with the hardwareon where to go next. Understanding where the current location is andwhere to go next greatly simplifies the problem of mapping the MCA, ACA,PCAs. The advantage of approach is that it identifies asymmetriesautomatically in not only flow velocity but waveform morphology.

F. Transducer Force Controller

One component often overlooked is the force required to maintainsufficient pressure of the transducer to the skin of the subject. Whenthe transducer is at an extreme angle insufficient pressure will allowthe transducer to slip, causing the loss of signal.

Some embodiments optimize TCD signal strength with a force sensingrobot. Normal force to the head is achieved in current mechanisms in anuncontrolled fashion, such as being manually screwed in. By using aforce sensor (or motor torque sensing) some embodiments automaticallyadjust TCD pressure to maximized signal strength. By sensing moments(torques) about the transducer, the surface normal orientation can bededuced. The condition for normal orientation is to minimize the momentsabout the transducer.

Curved Surface Following: Maintaining Transducer Orientation withConstant Force:

In order to generalize an automated TCD system from two dimensionalsurfaces to contoured heads, some embodiments provide mechanical androbotic controls to align the transducer normal to the surface whileapplying constant force. This work occurs in parallel with the TCDsearch and signal processing algorithm.

G. Kinematics

According to various embodiments, a five actuated degree of freedom(DOF) kinematic mechanism is used that fully automates evaluation of thetemporal window quality and can rediscover the temporal window evenafter complete loss of signal. To those skilled in the art, adistinction exists between an active, or actuated degree of freedom, onthe one hand, and a passive degree of freedom on the other hand. Anactive, or actuated degree of freedom includes an actuator, such as forexample, a motor. A passive degree of freedom does not require such anactuator. In this specification, if the term “degree of freedom” is usedwithout being qualified as passive, the degree of freedom discussed ismeant to be an active or actuated degree of freedom. In someembodiments, a computer generates commands and directs the mechanism totranslate and reorient the probe along the surface of the head until acandidate signal is located. Once located, the probe is reoriented toincrease signal strength. In some embodiments, reducing the search timeof the automated system to discover the temporal window is accomplishedby aligning the mechanism and probe at a known anatomical feature, suchas the zygomatic arch. In some embodiments, the alignment is performedwith a visual window guide for the user to place the probe at an initialstarting point along the zygomatic arch between ear and the eye.

In some embodiments, after the probe is properly aligned, the stiffnessof the probe is held normal to the surface at a high enough level tokeep the probe seated, but low enough so to be comfortable to the useras the probe moves in and out following the surface of the head. In someembodiments, the X and Y axes can retain a higher servo stiffness inorder to maintain precision control of probe location. In someembodiments, because the normal force of the probe is determined by theZ-axis stiffness, the sliding force encounter by the X and Y axes willbe limited to a comfortable level, and the probe can be directed toperform a search for the TCD window. In some embodiments, if theorientation of the probe needs to be changed, the orientationstiffnesses can be increased via software.

In some embodiments, the kinematic mechanism of the probe includes fivemotor, or actuated, degrees of freedom, Q={J1, J2, J3, J4, J5) (i.e.,motor or joint space) to effect five degrees of freedom in position andorientation X={x, y, z, pan, tilt} (i.e., task space). As such, theforward kinematics may be written as the relationship between motorcoordinates and probe coordinates: X=fwd_kin(Q), where fwd_kin is afunction representing a series of equations based on the mechanismdesign and typically analyzed by Denavit-Hartenberg parameters.

In some embodiments, placement of the TCD probe is specified via theinverse kinematics with either an analytic inverse solution:Q=inv_kin(X), or by using a numerical differential such as the Jacobianinverse solution dQ_(cmd)(n)=J⁻¹(X_(err)(n)), where J is the Jacobian,relating differential motion of the motors to the differential motion ofthe probe, X_(err)(n) is the probe position and orientation error attime n, and dQ_(cmd)(n) is the differential motor command at time n. Formechanisms with more motor or actuated degrees of freedom than probeposition and orientation coordinates being controlled, the kinematicsare called redundant, and such mechanisms have more than five motors.For redundant mechanisms, the inverse kinematics changes from theinverse Jacobian to the Moore-Penrose pseudo-inverse (or othergeneralized inverse) of the Jacobian, dQ_(cmd)(n)=J^(†)(X_(err)(n)).

FIG. 25 is a diagram of a model of a virtual support structure 4010 fora probe 4020, according to an exemplary embodiment. When probe 4020 isdiscussed, a transducer could be used instead. The support structure4010 is configured to position the probe 4020 relative to a targetsurface 4022. In some embodiments, the probe 4020 is a medical probe,such as a medical probe for use with a transcranial Doppler (TCD)apparatus to emit ultrasound wave emissions directed to the targetsurface 4022. In other embodiments, the probe 4020 is configured to emitother types of waves during operation, such as, but not limited to,infrared waves, x-rays, and so on. In various embodiments, the probe4020 may be a transcranial color-coded sonography (TCCS) probe, or itmay be an array such as a sequential array or phased array which emitswaves.

In some embodiments, the probe 4020 has a first end 4020 a and a secondend 4020 b. In some embodiments, the first end 4020 a interfaces withthe support structure 4010. In some embodiments, the second end 4020 bcontacts the target surface 4022 on which the probe 4020 operates at acontact point 4021. In some embodiments, the second end 4020 b is aconcave structure such that the contact point 4021 is a ring shape(i.e., the second end 4020 b contacts the target surface 4022 along acircular outer edge of the concave second end 4020 b). The supportstructure 4010 controls the relative position of the probe 4020 (e.g.,z-axis force, y-axis force, x-axis force, normal alignment, etc.). Thesupport structure 4010 is shown as a virtual structure including a firstvirtual spring 4011 coupled between the probe 4020 and a virtual surface4012 and exerting a force along a z-axis 4013, a second virtual spring4014 coupled between the probe 4020 and a virtual surface 4015 andexerting a force along a y-axis 4016, and a third virtual spring 4017coupled between the probe 4020 and a virtual surface 4019 and exerting aforce along the x-axis 4018. The virtual support structure 4010 furtherincludes a torsional spring 4023 exerting a torque about a tilt axis4027 and a second torsional spring 4025 exerting a torque about a panaxis 4029. In some embodiments, the virtual support structure 4010includes other virtual elements, such as virtual dampers (not shown).Virtual dampers represent elements that improve the stability of thesystem and are useful for tuning the dynamic response of the system. Thevirtual, or apparent inertia of the probe, can also be set to haveisotropic or anisotropic properties, by modeling and feed forwarding outthe effects of mechanism inertia, motor rotational inertial,centripetal/centrifugal effects, and replacing them with arbitraryinertial properties, within the physical performance limits of thedevice.

The virtual support structure 4010 represents a variety of mechanicalstructures that may be utilized to position the probe 4020 relative tothe target surface 4022, as described in more detail below. In someembodiments, the second end 4020 b of the probe 4020 is caused tocontact a relatively delicate surface, such as the skin of the patientor subject. The support structure is configured to adjust its stiffness(e.g., impedance, compliance, etc.) to provide variable linear forcesand rotational forces on the probe 4020, and may be relatively stiff insome directions and may be relatively compliant in other directions. Forexample, the support structure 4010 may apply minimal force and may berelatively compliant along the z-axis 4013 to minimize forces applied tothe patient or subject (e.g., if the patient or subject moves relativeto the support structure) in a direction generally normal to the targetsurface 4022 and may be relatively stiff along the y-axis 4016 and thex-axis 4018 to improve the positional accuracy and precision of theprobe 4020 along a plane generally parallel to the target surface 4022.Further, the desired stiffness of the support structure 4010 alongvarious axes may vary over time, depending on the task at hand. Forexample, the support structure may be configured to be relativelycompliant in scenarios in which the support structure 4010 is beingmoved relative to the patient or subject (e.g., during initial set-up ofthe probe structure, removal of the probe structure, etc.), or when itis advantageous to be relatively free-moving (e.g., duringmaintenance/cleaning, etc.), and may be configured to be relativelystiff, in some directions, in scenarios in which accuracy and precisionof the positioning of the probe 4020 is advantageous (e.g., during theTCD procedure or other procedure being performed with the probe 4020).

As described in more detail below, a kinematic model of the supportstructure 4010 can be utilized to calculate the relationship between theforces applied to the target surface 4022 by the probe 4020 and theforces (e.g., torques) applied by actuators actuating the supportstructure 4010. The forces applied to the target surface 4022 by theprobe 4020 in the idealized system can therefore be determinedtheoretically, without direct force sensing, thereby eliminating theneed for a load cell disposed in-line with the probe 4020 and/or a forcetorque sensor coupled to the probe 4020 to maintain appropriate contactforce that maximizes signal quality. In a physical system, staticfriction, along with other unmodeled physical effects, may introducesome uncertainty.

Referring to FIG. 26, the probe 4020 is shown according to an exemplaryembodiment mounted to a portion of a support structure, shown as agimbal structure 4024, which can rotate about multiple axes, at thefirst end 4020 a. The gimbal structure 4024 includes a first framemember 4026 that is able to rotate about the tilt axis 4027 and a secondframe member 4028 that is able to rotate about the pan axis 4029. Thetarget surface 4022 may be uneven (e.g., non-planar). The gimbalstructure 4024 allows the probe 4020 to be oriented such that it isnormal to the target surface 4022 at the contact point 4021.

Referring now to FIG. 27, FIG. 28, and FIG. 29, a support structure 4030for the probe 4020 is shown according to an exemplary embodiment as atwo-link revolute (e.g., revolute-revolute) robot. The support structure4030 includes a first frame member 4032, a second frame member 4034, athird frame member 4036, a fourth frame member 4038, and the gimbalstructure 4024. The first frame member 4032 is configured to be a staticmember. The first frame member 4032 may, for example, be mounted to ahalo or headset 4033 worn on the patient's or subject's head or otherstructure that attaches the first frame member 4032 to the patient orsubject or fixes the position of the first frame member 4032 relative tothe patient or subject. The probe 4020 is configured to emit energy intothe head of the patient or subject.

Referring to FIG. 27, the second frame member 4034 is a link configuredto rotate about the z-axis 4013. The z-axis 4013 is generallyperpendicular to the surface of the head. A first end 4040 of the secondframe member 4034 is coupled to the first frame member 4032. Accordingto an exemplary embodiment, the rotation of the second frame member 4034relative to the first frame member 4032 is controlled by an actuator4042, shown as an electric motor and gearbox that is attached throughthe first frame member 4032. Actuator 4042 acts as a perpendiculartranslation actuator for translating the probe along a perpendicularaxis generally perpendicular to the surface of the head.

The third frame member 4036 is a link configured to rotate about thez-axis 4013. A first end 4044 of the third frame member 4036 is coupledto a second end 4046 of the second frame member 4034. According to anexemplary embodiment, the rotation of the third frame member 4036relative to the second frame member 4034 is controlled by an actuator4048, shown as an electric motor and gearbox that is attached throughthe second frame member 4034.

The fourth frame member 4038 is configured to translate along the z-axis4013 (e.g., in and out, in and away from the head, etc.). According toan exemplary embodiment, the fourth frame member 4038 slides along railmembers 4050 that are fixed to a second end 4052 of the third framemember 4036. The position of the fourth frame member 38 relative to thethird frame member 4036 is controlled by an actuator, such as anelectric motor and a lead screw (not shown for clarity).

The gimbal structure 4024 and the probe 4020 are mounted to the fourthframe member 4038. The gimbal structure 4024 controls the orientation ofthe probe 4020 about the tilt axis 4027 and the pan axis 4029 (e.g., panand tilt). The position of the probe 4020 about the tilt axis 4027 iscontrolled by an actuator 4054, shown as an electric motor and gearbox.Actuator 4054 acts as a rotation actuator to rotate the probe. Theposition of the probe 4020 about the pan axis 4029 is controlled by anactuator 4056, shown as an electric motor and gearbox. Actuator 4056acts as a rotation actuator to rotate the probe. In one embodiment, therotation of the probe 4020 about the tilt axis 4027 and the pan axis4029 is different than the z-axis 4013, regardless of the rotation ofthe frame members 4034 and 4036.

The probe 4020 is able to move on the x-y plane, i.e., the translationplane, which is defined by the x-axis 4018 and the y-axis 4016, throughthe rotation of the second frame member 4034 and the third frame member4036. The probe 4020 is able to move along the z-axis 4013, i.e., thetranslation axis, through the translation of the fourth frame member4038. Further, the probe 4020 is able to rotate about tilt axis 4027 andthe pan axis 4029 through the gimbal structure 4024. Combining thesefive actuated degrees of freedom allows the position and orientation ofthe probe 4020 relative to the target surface 4022 to be completelydescribed and controlled, discounting rotation about a third axis thatis orthogonal to the pan axis 4029 and the tilt axis 4027.

According to an exemplary embodiment, the actuators utilized to positionthe support structure 4030 are servo motors. The use of servo motors tocontrol the support structure allow for a more precise control, comparedto a stepper motor, for the torque output, rotational position, andangular speed of the motor, as well as the corresponding position of theprobe 4020 and the interaction between the probe 4020 and the targetsurface 4022. Of course, other suitable motors known to those ofordinary skill in the art could also be used.

Referring now to FIG. 30, FIG. 31, and FIG. 32, a support structure 4060for the probe 4020 and the gimbal structure 4024 is shown according toanother exemplary embodiment as a prismatic (e.g., Cartesian,rectilinear, etc.) robot. FIG. 30 illustrates an exemplaryPrismatic-Prismatic-Prismatic robot. The support structure 4060 includesa first frame member 4062, a second frame member 4064, a third framemember 4066, a fourth frame member 4068, and the gimbal structure 4024.The first frame member 4062 is configured to be a static member. Thefirst frame member 4062 may, for example, be mounted to a halo orheadset 4033 worn on the patient's or subject's head or other structurethat fixes the position of the first frame member 4062 relative to thepatient or subject.

The second frame member 4064 is configured to translate along the y-axis4016 (e.g., up and down, bottom of ear to top of ear, etc). According toan exemplary embodiment, the second frame member 4064 slides along railmembers 4070 that are fixed to the first frame member 4062. The positionof the second frame member 4064 relative to the first frame member 4062is controlled by an actuator, such as an electric motor and a lead screw(not shown for clarity).

The third frame member 4066 is configured to translate along the x-axis4018 (e.g., forward and backward, ear to eye, etc.). According to anexemplary embodiment, the third frame member 4066 slides along railmembers 4072 that are fixed to the second frame member 4064. The railmembers 4072 are orthogonal to the rail members 4070. The position ofthe third frame member 4066 relative to the second frame member 4064 iscontrolled by an actuator, such as an electric motor and a lead screw(not shown for clarity).

The fourth frame member 4068 is configured to translate along the z-axis4013 (e.g., in and out, in and away from the head, etc.). According toan exemplary embodiment, the fourth frame member 4068 slides along railmembers 4074 that are fixed to the third frame member 4066. The positionof the fourth frame member 4068 relative to the third frame member 4066is controlled by an actuator, such as an electric motor and a lead screw(not shown for clarity).

The gimbal structure 4024 and the probe 4020 are mounted to the fourthframe member 4068. The gimbal structure 4024 controls the orientation ofthe probe 4020 about the tilt axis 4027 and the pan axis 4029 (e.g.,tilt and pan). The position of the probe 4020 about the tilt axis 4027is controlled by an actuator 4084, shown as an electric motor andgearbox. The position of the probe 4020 about the pan axis 4029 iscontrolled by an actuator 4086, shown as an electric motor and gearbox.

The probe 4020 is able to move on the x-y plane through the translationof the second frame member 4064 and the third frame member 4066, movealong the z-axis 4013 through the translation of the fourth frame member4068, and rotate about tilt axis 4027 and the pan axis 4029 through thegimbal structure 4024. Combining these five actuated degrees of freedomallows the position and orientation of the probe 4020 relative to thetarget surface 4022 to be completely described and controlled,discounting rotation about a third axis that is orthogonal to the panaxis 4029 and the tilt axis 4027.

A kinematic model can be developed for any embodiment of a supportstructure for the probe 4020 to determine the relationship between theforces exerted at the probe 4020 and the forces applied by the actuatorscontrolling the support structure.

A stiffness matrix for the support structure is first determined. Thestiffness matrix is determined using a multitude of variables, includingthe physical properties of the support structure (e.g., the geometry ofthe frame members, the stiffness of the individual frame members etc.),the system stiffness along the chosen coordinate system axis, and avelocity-based term for system damping. According to an exemplaryembodiment, the desired stiffness of the support structure is defined inthe z direction (K_(z)), the y direction (K_(y)), and the x direction(K_(x)) (e.g., as represented by the virtual springs 4011, 4014, and4017 in FIG. 25), and about the pan axis 4029 (Kω_(x)) and about thetilt axis 4027 (Kω_(y)) (e.g., as represented by the virtual torsionalsprings 4023 and 4025 in FIG. 25). As described above, in someembodiments, the virtual stiffnesses vary over time and are based on thetask being accomplished with the probe 4020. For example, stiffness inthe y direction and in the x direction may have a lower boundcorresponding to a relatively low lateral stiffness during a set-up orremoval procedure, in which the support structure is configured to berelatively compliant; and an upper bound corresponding to a relativelyhigh stiffness during a scanning procedure, in which the supportstructure is configured to be relatively stiff, allowing for a moreaccurate positioning of the probe 4020. Likewise, stiffness in the zdirection may have a lower bound corresponding to a relatively lowstiffness during initial positioning of the probe 4020 in the zdirection, in which the support structure is configured to be relativelycompliant to allow the probe 4020 to self-align (e.g., to minimizediscomfort for the patient or subject); and an upper bound correspondingto a relatively high stiffness during a scanning procedure, in which thesupport structure is configured to more stiff, to overcome frictionforces between the probe 4020 and the target surface 4022 and tomaintain the orientation of the probe 4020. Further, rotationalstiffnesses about the y axis and the x axis may have a lower boundcorresponding to a relatively low rotational stiffness duringpositioning of the probe 4020 to conform to the contour of the targetsurface 4022 (e.g., the head of the patient or subject), in which thesupport structure (e.g., the gimbal structure 4024) is configured to berelatively compliant (e.g., to minimize discomfort for the patient orsubject); and an upper bound corresponding to a relatively highrotational stiffness when a more accurate positioning (e.g., panning,tilting, etc.) of the probe 4020 is desired.

A force vector is then derived using the following equation:

{right arrow over (F)}=KΔ{right arrow over (x)}   (Eq. 16)

where K is the stiffness matrix and Δ{right arrow over (x)} is thevector of the difference of the desired and actual translationalposition in the x, y, and z directions and rotational position about thex-axis 404018 and y-axis 16 of the probe 4020.

The force applied by the actuators (e.g., the torque applied byrotational actuators) controlling the position of the support structuremay then be determined using the following equation:

τ=J ^(T) {right arrow over (F)}   (Eq. 17)

where J^(T) is the Jacobian transpose determined by the kinematics ofthe specific support structure. The Jacobian is the differentialrelationship between the joint positions and the end-effector positionand orientation (e.g., the position of the probe 4020). The jointpositions are either in units of radians (e.g., for rotational joints),or in units of length (e.g., for prismatic or linear joints). TheJacobian is not static and changes as the support structure positionarticulates.

Referring now to FIG. 29, a schematic front view diagram of the supportstructure 4030 is shown. The second frame member 4034 is represented bya first link 4090, having a length l₁. The first link 4090 isarticulated by a rotary actuator 4094, the rotation of which is shown asq₁. The third frame member 4036 is represented by a second link 4092,having a length l₂. The second link 4092 is articulated by a rotaryactuator 4096, the rotation of which is shown as q₂. The actuators 4094and 4096 move the probe 4020 in the x-y plane.

The forward kinematics of this device are:

c ₁=cos(q ₁),s ₁=sin(q ₁)

C ₁₂=cos(q ₁ +q ₂),s ₁₂=sin(q ₁ +q ₂)

x=l ₁ c ₁ +l ₂ c ₁₂   (Eq. 18)

y=l ₁ s ₁ +l ₂ s ₁₂   (Eq. 19)

The Jacobian for such a revolute-revolute robot is derived by taking thepartial derivative of the forward kinematics with respect to both q₁ andq₂.

$\begin{matrix}{J = \begin{bmatrix}{{{- l_{1}}s_{1}} - {l_{2}s_{12}}} & {{- l_{2}}s_{12}} \\{{l_{1}c_{1}} + {l_{2}c_{12}}} & {l_{2}c_{12}}\end{bmatrix}} & \left( {{Eq}.\; 20} \right)\end{matrix}$

The Jacobian shown in Eq. 20 is the Jacobian for the Cartesian movementof the revolute-revolute robot on the x-y plane (e.g., translation alongthe y-axis 4016 and the x-axis 4018), describing the differentialrelationship between joint motion and probe motion. One of ordinaryskill in the art would understand that in other embodiments, additionalterms may be included in the Jacobian to describe the differentialrelationship between the motion of the probe 4020 and other motions ofthe robot (e.g., rotation of the probe 4020 about the tilt axis 4027 andthe pan axis 4029 and translation along the z-axis 4013).

Referring now to FIG. 30, a schematic front view diagram of the supportstructure 4060 is shown. The probe 4020 is moved in the y direction by afirst linear actuator 4100 (e.g., an electric motor and lead screw) andis moved in the x direction by a second linear actuator 4102 (e.g., anelectric motor and lead screw). The actuators 4100 and 4102 move theprobe 4020 in the x-y plane. Because each joint is orthogonal to theother, and has a one to one mapping of joint motion to Cartesian motion,the Jacobian for such a prismatic robot becomes the identity matrix:

$\begin{matrix}{J = \begin{bmatrix}1 & 0 \\0 & 1\end{bmatrix}} & \left( {{Eq}.\; 21} \right)\end{matrix}$

The Jacobian shown in Equation 21 is the Jacobian for the Cartesianmovement of the prismatic robot on the x-y plane (e.g., translationalong the y-axis 4016 and the x-axis 4018), describing the differentialrelationship between joint motion and probe motion. In otherembodiments, additional terms may be included in the Jacobian todescribe the differential relationship between the motion of the probe4020 and other motions of the robot (e.g., rotation of the probe 4020about the tilt axis 4027 and the pan axis 4029 and translation along thez-axis 4013).

Referring to FIG. 27, The support structure 4030 controls the positionof the probe 4020 in the z direction with the translation of the fourthframe member 4038 with a single linear actuator (e.g., an electric motorand lead screw). Referring to FIG. 30, Similarly, the support structure4060 controls the position of the probe 4020 in the z direction with thetranslation of the fourth frame member 4068 with a single linearactuator (e.g., an electric motor and lead screw). For either supportstructure, there is a direct correlation between the position of theactuator and the position of the probe 4020.

Referring now to FIG. 35, a method 4110 of determining the input force,or torque, for an actuator for a probe support structure is shownaccording to an exemplary embodiment. The configuration of the supportstructure for a probe is first determined (step 4112). The configurationmay include any number of revolute joints and/or prismatic joints. Insome embodiments, the support structure provides translation of theprobe along one or more axis (e.g., the x, y, and z axis in a Cartesiancoordinate system; the r, θ, and z axis in a polar coordinate system,etc.) and/or rotation about one or more axis.

Based on the configuration of the support structure and the desiredvariable stiffness of the support structure, a stiffness matrix for thesupport structure is determined (step 4114). The stiffness matrixincludes terms based on the physical properties of the supportstructure, including the geometry of the frame members and the stiffnessof the individual frame members, the desired stiffness of the supportstructure in the z direction (Kz), the y direction (Ky), and the xdirection (Kx), the desired rotational stiffness of the supportstructure (Kω_(x), Kω_(y)), and a velocity-based term for systemdamping.

Based on the stiffness matrix and the desired translational androtational position of the probe, a force vector is determined (step4116). The desired position of the probe may be determined using anycoordinate system. According to an exemplary embodiment, the forcevector is derived from the product of the stiffness matrix and a matrixof the desired translational and rotational position of the probe, asshown in Equation 1.

The Jacobian for the support structure is then calculated (step 4118).The Jacobian is determined by the kinematics of the specific supportstructure. The Jacobian is the differential relationship between thejoint positions and the end-effector position. The joint positions areeither in units of radians (e.g., for rotational joints), or in units oflength (e.g., for prismatic or linear joints). The Jacobian is notstatic and changes as the support structure position articulates.

Based on the force vector and the Jacobian, the input force for theactuator is determined (step 4120). According to an exemplaryembodiment, the input force for the actuator is derived from the productof the Jacobian and the force vector, as shown in Eq. 17.

Referring now to FIG. 36, FIG. 37, and FIG. 38, a support structure 4130for the probe 4020 is shown according to another exemplary embodiment asa five-link revolute robot. The support structure 4130 includes a firstframe member 4132; a pair of proximal members coupled to the first framemember 4132, shown as a second frame member 4134 a and a third framemember 4134 b; a pair of distal members coupled to the respectiveproximal frame members and to each other, shown as a fourth frame member4136 a and a fifth frame member 4136 b; a sixth frame member 4138coupled to the distal frame members; and the gimbal structure 4024. Thefirst frame member 4132 is configured to be a static member. The firstframe member 4132 may, for example, be mounted to a halo or headset 4033worn on the patient's or subject's head or other structure that fixesthe position of the first frame member 4132 relative to the patient orsubject.

The second frame member 4134 a and the third frame member 4134 b arelinks configured to rotate about the z-axis 4013. A first end 4140 a ofthe second frame member 4134 a is coupled to the first frame member4132. Similarly, a first end 4140 b of the third frame member 4134 b iscoupled to a separate portion of the first frame member 4132. Accordingto an exemplary embodiment, the rotation of the second frame member 4134a relative to the first frame member 4132 is controlled by an actuator4142 a, shown as an electric motor and gearbox that is attached throughthe first frame member 4132. According to an exemplary embodiment, therotation of the third frame member 4134 b relative to the first framemember 4132 is controlled by an actuator 4142 b, shown as an electricmotor and gearbox that is attached through the first frame member 4132.

The fourth frame member 4136 a and the fifth frame member 4136 b arelinks configured to rotate about the z-axis 4013. A first end 4144 a ofthe fourth frame member 4136 a and a second end 4146 a of the secondframe member 4134 a are each coupled to a hub member 4148 a via bearings(e.g., press fit bearings, etc.). Similarly, a first end 4144 b of thefifth frame member 4136 b and a second end 4146 b of the third framemember 4134 b are each coupled to a hub member 4148 b via bearings(e.g., press fit bearings, etc.).

The fourth frame member 4136 a and the fifth frame member 4136 b arecoupled together via a bearing (e.g., a press fit bearing, etc.) to forma five-bar linkage. The hub members 4148 a and 4148 b offset theproximal members from the distal members along the z-axis 4013, whichallows the proximal frame members (e.g., second frame member 4134 a andthird frame member 4134 b) to move freely past the distal frame members(e.g., fourth frame member 4136 a and fifth frame member 4136 b) as thelinks are rotated by the actuators 4142 a and 4142 b.

The gimbal structure 4024 and the probe 4020 are mounted to the sixthframe member 4138. The sixth frame member 4138 is coupled to one of thedistal members (e.g., fourth frame member 136 a or fifth frame member4136 b) and is configured to translate the gimbal structure 4024 and theprobe 4020 along the z-axis 4013 (e.g., in and out, in and away from thehead, etc.). The sixth frame member 4138 may translate, for example, onrails, as described above in regards to the fourth frame member 4038 ofthe support structure 4030 (see FIG. 36, FIG. 37, FIG. 38). The gimbalstructure 4024 controls the orientation of the probe 4020 about the tiltaxis 4027 and the pan axis 4029 (e.g., pan and tilt). The position ofthe probe 4020 about the tilt axis 4027 is controlled by an actuator(not shown), such as an electric motor and gearbox. The position of theprobe 4020 about the pan axis 4029 is controlled by an actuator (notshown), such as an electric motor and gearbox. In one embodiment, therotation of the probe 4020 about the tilt axis 4027 and the pan axis4029 is different than the z-axis 4013, regardless of the rotation ofthe frame members 4134 and 4136.

The probe 4020 is able to move on the x-y plane through the movement ofthe five-bar linkage formed by the first frame member 4132, the secondframe member 4134 a, the third frame member 4134 b, the fourth framemember 4136 a, and the fifth frame member 4136 b. The probe 4020 is ableto move along the z-axis 4013 through the translation of the sixth framemember 4138. Further, the probe 4020 is able to rotate about tilt axis4027 and the pan axis 4029 through the gimbal structure 4024. Combiningthese five actuated degrees of freedom allows the position andorientation of the probe 4020 relative to the target surface 4022 to becompletely described and controlled, discounting rotation about a thirdaxis that is orthogonal to the pan axis 4029 and the tilt axis 4027.

According to an exemplary embodiment, the actuators utilized to positionthe support structure 4130 are servo motors. Of course, any suitablemotors could be used instead of servo motors. The use of servo motors tocontrol the support structure allow for a more precise control, comparedto a stepper motor, over the rotational position and angular speed ofthe motor, as well as the corresponding position of the probe 4020 andthe interaction between the probe 4020 and the target surface 4022.

The input forces for the actuators 4142 a and 4142 b can be calculatedin a manner similar to that described above by determining the forcevector, determining the forward kinematics of the support structure4130, and calculating the Jacobian by taking the partial derivative ofthe forward kinematics with respect to the rotations of each of theactuators 4142 a and 4142 b.

In some embodiments, for probe 4020 contact and seating, instead oftrying to predict and control the exact position and orientation of theprobe 4020, the impedance of the probe 4020 is selectively controlled,whether by mechanical design or through software. As such, theorientation degrees of freedom of the probe 4020 can be compliant sothat they rotate against contact and seat the probe 4020 flush with thehead, while the translation degrees of freedom are stiff enough to movethe probe 4020 and keep it placed against the head. In some embodiments,each of the directions has different impedances.

In some embodiments, software is implemented to limit motor torque andmotor servo stiffness of the probe 4020. In some embodiments, there maybe different limits for each direction, creating different stiffnessesin different directions. In some embodiments, the pan and tilt are verycompliant, while the translational motions are moderately stiffer. Insome embodiments, stiffness through the probe 4020 is more compliantthan the X, Y translational degrees of freedom.

In some embodiments, software is implemented for task space impedancecontrol. In other words, there can be considered the probe 4020orientation to define a local coordinate system with the Z axis throughthe center of the probe 4020. Instead of manipulating the impedance ofthe probe 4020 by adjusting motor servo stiffness and torque limiting,in some embodiments, the kinematics of the entire robot can beconsidered to set the impedance of each of the five directions, X, Y, Z,pan, and tilt, local to the probe's 4020 coordinate frame. As such, theprobe 4020 can be more compliant through the center line of the probe4020, but still maintain contact with the surface of the skin, but havelocal X and Y stiffness sufficient to control the location of the probe4020 with precision.

According to various embodiments, the probe 4020 includes a serieselastic actuator. In some embodiments, the impedance of the device isaltered by adding a compliant member into the mechanical design, eitheras a spring element into the motor or as a structural member of therobot. In some embodiments, measurement of the amount of deflection isimplemented in order to measure the exact position and orientation ofthe probe 4020. A series elastic actuator has the benefit of beingdesigned to an exact compliance, and even has a damping element added,while avoiding computational nonlinearities and instabilities associatedwith programming the impedance.

In some embodiments, the force is indirectly measured by monitoring theapplied current of the motor. For the static case, taking into accountthe kinematics of the robot, the force/torque vector of the system iscomputed from the Jacobian: F=(J^(T))⁻¹τ, where τ is the vector of motortorques as predicted by the applied current to the motor.

In some embodiments, the interaction force and torque between the probe4020 and the head is controlled by placing a force/torque sensingmechanism behind the probe 4020. The position and orientation of theprobe is specified in relation to the measured forces and torques toachieve a desired force/torque vector. This type of closed loopcontroller is called admittance control and is programmed into thesoftware. Admittance control relates the measured force to a desiredprobe position and orientation, as illustrated in the followingequation.

{right arrow over (X)} _(desired) =G _(control) {right arrow over (F)}_(measured)

The desired position vector is used to compute desired joint positionsfrom the inverse kinematics. Motor joint controllers are programmed withhigh servo stiffness to enhance disturbance rejection and have low servotracking errors. A hybrid position-force admittance controller 4150 isillustrated in FIG. 39.

In this example of a hybrid position-force controller, force iscontrolled in the z direction of the probe, while position is controlledin the x and y directions, and the pan and tilt orientations. A hybridcommand of positions and force in task space,[x_(cmd),y_(cmd),F_(cmd),pan_(cmd),tilt_(cmd)] 4152, is sent by theprobe command input block 4154, which determines task oriented moves ofthe probe, such as searching. In this case the position and orientationis specified in x, y, pan and tilt, and is given in units of length andangle (mm and radians). Force is specified in the z direction, and isgiven in units of Newtons. For an admittance controller, the forcecommand must be transformed into a desired position. The force command,F_(cmd) 4156, is extracted from the probe input command block 4154 asused as the command for the admittance force control law block 4158.Using the measured force, F_(measured), a change in z position, Δz, iscomputed by the admittance force control law block 4158. A simple,single proportional gain controller is illustrated, but other controllerforms can be used. In the update z command position block 4160, Δz 4162is added to the old z command position to create an updated z command,Z_(cmd) 4164. This information is merged with the other probe positionand orientation commands in the reconcile probe command block 4166. Thereconciled command, R_(cmd) 4168 specifies the probe position andorientation in units of length and angle,[x_(cmd),y_(cmd),z_(cmd),pan_(cmd),tilt_(cmd)]. The inverse kinematicsblock 4170 uses the reconciled command, R_(cmd) 4168 to solve for thenew robot joint command position, q_(cmd) 4172, based on the mechanicsof the specific robot. It is understood from the discussion above thatthe robot could have a direct analytic inverse solution, or a numericalsolution based on the inverse or pseudo inverse Jacobians depending onthe number of degrees of freedom.

The joint command position, q_(cmd) 4172, is used as the input for theinner position control loop comprised of the joint motor controllersblock 4174, the output torques 4176, robot mechanics block 4178, whichis the physical robot, and the measured joint positions, q 4180. Therobot mechanics block 4178 also includes a force sensor which outputsthe measured force, F_(measured) 4182. The measured force, F_(measured)4182 is the second input to the admittance force control law block 4158,which closes the force control loop.

The measured joint positions, q 4180, are used as the to the calculateforward kinematics block 4184, which computes the current probe positionand orientation [x,y,z,pan,tilt] 4186, and sends it back to the probecommand input block 4154, for use in its probe command generationalgorithm.

When combined with an impedance law, different directional andorientational stiffnesses at the probe 4020 can be programmed.Admittance control is appropriate for non-backdriveable motors, whichare more difficult to use with pure impedance controllers because,without a force-torque sensor, the static friction resisting the user isunobservable while at rest.

Other configurations of the support structure include over and underactuated mechanisms. An over-actuated mechanism, or redundantmanipulator, includes more actuated degrees of freedom than task spacecoordinates that are attempted to be controlled; e.g., the number ofmotors, Q={J1, J2, J3, J4, J5, . . . ) is greater than the five degreesof freedom in position and orientation X={x, y, z, pan, tilt} of theprobe that is being controlled. For such mechanisms there will be many,and possibly an infinite number, of inverse kinematic solutions.

An example of an over-actuated mechanism, or redundant manipulator, isthe UR3 Robot, made by Universal Robots, which has six rotating joints,each controlled by its own actuator or motor, to allow for six actuateddegree of freedom movement.

Referring now to FIG. 40, FIG. 41, and FIG. 42, an under actuated system4300 is shown. Such a system has four actuated degrees of freedom in thex,y,pan,tilt axes and a spring providing force along the z axis. In theunder actuated system 4300 shown, the system has fewer than fiveactuated degrees of freedom, but is still capable of performing the TCDpositioning task. The under actuated system 4300 shown is a fouractuated degree of freedom mechanism that can position and orient theprobe 4020 in X={x, y, pan, tilt}. In the under actuated system 4300, aspring 4302 exerts force on the probe 4020 along a z-axis 4013. In fiveactuated degree of freedom systems the force exerted by the spring inunder actuated system 4300 would be actuated by a motor drivenmechanism. The gimbal structure 4024 allows the probe 4020 to beoriented. The force in the z-axis 4013 is in effect, monitored by thecharacterization of the spring constant associated with the spring 4302.The actuation in the x-axis 4018 is controlled by actuator 3404 shown asan electric motor and lead screw. The actuation in the y-axis 4016 iscontrolled by actuator 4306 shown as an electric motor and lead screw.The actuation in the pan axis 4029 is controlled by motor 4308. Theactuation in the tilt axis 4027 is controlled by motor 4310.

Referring now to FIG. 43, FIG. 45, and FIG. 45 a support structure 4400is shown for the probe 4020 and the gimbal structure 4024 is shownaccording to another exemplary embodiment as a prismatic (e.g.,Cartesian, rectilinear, etc.) robot. The support structure 4400 may, forexample, be mounted to a halo or headset 4033 worn on the patient's orsubject's head or other structure. The support structure 4400 includes acover 4401 that covers some of the mechanisms of the support structure4400. In FIG. 45, an exploded view of support structure 4400 shows thecover 4401 taken off the support structure 4400.

A first motor 4402 is configured to use a first spur gear 4403 toactuate a lead screw 4405 mechanism. The first spur gear 4403 is coupledto a second spur gear 4404 which converts rotational motion of the firstmotor 4402 into linear motion along lead screw 4405 to translate theprobe 4020 along a y-axis 4016 (e.g., up and down, bottom of ear to topof ear, etc). A second motor 4406 is configured to use a third spur gear4407 coupled to a fourth spur gear 4408, which in turn is coupled to arack and pinion mechanism 4409 to translate the probe 4020 along az-axis 4013 towards and away from the head of a subject. As shown, inFIG. 44, a third motor 4412 and bearing 4410 allow for rotation of thegimbal 4024 about a tilt axis 4027, which in this embodiment, isparallel to x-axis 4018. A plate 4414 houses two linear rails 4416, 4418and allows for mounting of a fourth motor (not shown for clarity) totranslate along the x-axis 4018 (e.g., forward and backward, ear to eye,etc.). As shown in FIG. 45, a fifth motor 4420 allows for controllingrotation of the gimbal 4024 about pan axis 4029, which, in thisembodiment is parallel to y-axis 4016, thus completing the necessarydegrees of freedom to define five degree of freedom actuated roboticsystem.

H. Surface Alignment

FIG. 46 illustrates a front perspective view of a remote center ofcompliance (RCC) probe device 5100 according to various embodiments.FIG. 47 illustrates a rear view of the RCC probe device 5100 accordingto various embodiments. Referring to FIG. 46 and FIG. 47, in someembodiments, the RCC probe device 5100 includes a probe 5102, an RCCassembly 5150, and a load cell 5104.

In some embodiments, the probe 5102 includes a first end 5102 a and asecond end 5102 b that is opposite to the first end 5102 a. In someembodiments, the first end 5102 a includes a concave surface 5103 thatis configured to be adjacent to or contact a scanning surface. Theconcave surface 5103 is configured with a particular pitch to focusgenerated energy towards the scanning surface. In some embodiments, theRCC probe device 5100 is a Transcranial Doppler (TCD) apparatus suchthat the first end 5102 a of the probe 5102 is configured to be adjacentto or contact and align along a human head (e.g., a side of the humanhead), and the first end 5102 a of the probe 5102 is configured toprovide ultrasound wave emissions from the first end 5102 a and directedinto the human head (e.g., towards the brain). In other embodiments, theprobe 5102 is configured to emit other types of waves during operation,such as, but not limited to, infrared waves, x-rays, or the like.

In some embodiments, the second end 5102 b of the probe 5102 is coupledto the RCC assembly 5150. In some embodiments, the probe 5102 isconnected to the RCC assembly 5150 via a connection interface 5106 thatinterposes the RCC assembly 5150 and the probe 5102. In someembodiments, the second end 5102 b of the probe 5102 includes a threadedsection along a portion of the body of the probe 5102, and the secondend 5102 b is configured to be secured in the connection interface 5106via the threads (e.g., by being screwed into the connection interface5106). In other embodiments, the probe 5102 is secured in the connectioninterface 5106 by any other suitable connecting means, such as, but notlimited to, welding, adhesive, one or more hooks and latches, one ormore separate screws, press fittings, or the like.

In some embodiments, the connection interface 5106 is connected to theRCC assembly 5150 by use of separate connecting members. In someembodiments, the connecting members are a plurality of screws, and theRCC assembly 5150 includes corresponding threaded holes for receivingthe plurality of screws. In other embodiments, the connection interface5106 is secured in the RCC assembly 5150 by any other suitableconnecting means, such as, but not limited to, welding, adhesive, one ormore hooks and latches, or the like. Accordingly, in some embodiments,the connection interface 5106 provides a means for connecting andsecuring the probe 5102 to the RCC assembly 5150.

In some embodiments, the load cell 5104 is coupled to the probe 5102. Insome embodiments, the load cell 5104 is configured to take measurementsof pressure or force exerted on the load cell 5104. In some embodiments,because the load cell 5104 is adjacent to or contacting the probe 5102(e.g., via the connection interface 5106), a force exerted against theconcave surface 5103 of the first end 5102 a of the probe 5102 (e.g.,caused by the concave surface 5103 being pressed against a human head),is registered at the load cell 5104 and can be measured by the load cell5104.

In some embodiments, the load cell 5104 is a transducer that is used tocreate an electrical signal whose magnitude is proportional to the forcebeing measured. In some embodiments, wires extending from the load cell5104 provide electrical signals emanating from the load cell 5104,responsive to the force on the load cell 5104 caused by the probe 5102.During operation, in some embodiments, when the probe 5102 is pressedagainst a human skull, a force will also be imparted through theconnection interface 5106 to the load cell 5104, which can be measuredby the load cell 5104.

Accordingly, in some embodiments, the RCC probe device 5100 utilizes themeasurements of the load cell 5104 to adjust the pressure exerted by theprobe 5102. For example, in some embodiments, the RCC probe device 5100decreases the force exerted against a human head by the probe 5102 whenthe pressure measured by the load cell 5104 is determined to berelatively high (e.g., the pressure measurement exceeds a predeterminedthreshold).

According to various embodiments, the RCC probe device 5100 is capableof fitting and functioning with a table-top robot, such as, but notlimited to, the UR3 collaborative table-top robot, and the RCC probedevice 5100 is adapted to fit into an end effector of the robot.

In some embodiments, the load cell 5104 indirectly contacts the probe5102 via the connection interface 5106, or, in other words, theconnection interface 5106 is interposed between the probe 5102 and theload cell 5104. Accordingly, in some embodiments, the connectioninterface 5106 is made of a suitable material for transmitting thepressure forces against the probe 5102 to the load cell 5104, such as,but not limited to, a non-metal material (e.g., polyurethane) and thelike. Moreover, in some embodiments, the connection interface 5106 hasany suitable shape for transmitting forces to the load cell 5104 fromthe probe 5102, such as, but not limited to, a bridge or the like.

In some embodiments, the load cell 5104 is positioned to be housedwithin the RCC assembly 5150. In such embodiments, the RCC assembly 5150includes an empty space therein to accommodate the load cell 5104 suchthat the form factor of the RCC probe device 5100 may be minimized. Inother embodiments, the load cell 5104 is positioned at any suitablelocation within the RCC probe device 5100 to measure the force exertedagainst the probe 5102. In one example, the load cell 5104 is locatedabove the RCC assembly 5150 and below the probe 5102 such that the loadcell 5104 interposes the probe 5102 and the RCC assembly 5150. Inanother example, the load cell 5104 is located below the RCC assemblysuch that the RCC assembly 5150 interposes the load cell 5104 and theprobe 5102.

FIG. 48 illustrates an exploded view of the RCC probe device 5100according to various embodiments. Referring to FIG. 46, FIG. 47, andFIG. 48, in some embodiments, the RCC assembly 5150 includes a firstplate 5151, a second plate 5152, and a plurality of compliant beams 5154a, 5154 b, 5154 c, and 5154 d interposed between the first plate 5151and the second plate 5152.

In some embodiments, the first plate 5151 has a substantially similarsize and shape to the size and shape of the second plate 5152. In someembodiments, the first plate 5151 and the second plate 5152 are circularshapes having substantially similar diameters, with each of the firstplate 5151 and second plate 5152 having a center point or origin. Inother embodiments, the first plate 5151 and the second plate 5152 areany other suitable shape, such as, but not limited to, squares,triangles, hexagons, or the like. In some embodiments, the first plate5151 has a circular hole at its center to allow a pathway for aconnection of the load cell 5104 to the connection interface 5106 andthe probe 5102. In some embodiments, the first plate 5151 and the secondplate 5152 each have a center point (e.g., an origin) aligned to bealong the same axis. In some embodiments, the first plate 5151 and thesecond plate 5152 are made from any suitable rigid material, such as,but not limited to, steel, iron, plastic, polyoxymethylene, aluminum, orthe like. In some embodiments, the first plate 5151 and the second plate5152 are made from the same material. In other embodiments, the firstplate 5151 and the second plate 5152 are made from different materials.

In some embodiments, the compliant beams include a first compliant beam5154 a, a second compliant beam 5154 b, a third compliant beam 5154 c,and a fourth compliant beam 5154 d. In other embodiments, any suitablenumber of compliant beams are used, such as, but not limited to, threecompliant beams, five compliant beams, or more. In some embodiments, thecompliant beams 5154 a, 5154 b, 5154 c, and 5154 d are made from anysuitable flexible material, such as, but not limited to, polyurethane,rubber, or the like. In some embodiments, the first compliant beam 5154a includes a top end 5155 and a bottom end 5156, and the top end 5155 iscoupled to the first plate 5151 and the bottom end 5156 is coupled tothe bottom plate 5152. Each of the second compliant beam 5154 b, thirdcompliant beam 5154 c, and fourth compliant beam 5154 d includes a topend 5155 and a bottom end 5156 arranged between the first plate 5151 andthe second plate 5152.

In some embodiments, each of the compliant beams 5154 a, 5154 b, 5154 c,and 5154 d is affixed to the first plate 5151 (e.g., via the top end5155) and to the second plate 5152 (e.g., via the bottom end 5156) byany suitable means of securing the compliant beams 5154 a, 5154 b, 5154c, and 5154 d, such as, but not limited to, welding, adhesive, one ormore hooks and latches, one or more separate screws, bolting, or thelike.

In some embodiments, the first plate 5151 includes a first hole 5151 a,a second hole 5151 b, a third hole 5151 c, and a fourth hole 5151 d, andeach of the first hole 5151 a, the second hole 5151 b, the third hole5151 c, and the fourth hole 5151 d creates an opening through the bodyof the first plate 5151. In some embodiments, the top end 5155 of eachof the compliant beams 5154 a, 5154 b, 5154 c, and 5154 d is coupled tothe first plate 5151 via the first hole 5151 a, the second hole 5151 b,the third hole 5151 c, and the fourth hole 5151 d, respectively. In someembodiments, corresponding connectors (e.g., screws) are positionedthrough the holes 5151 a, 5151 b, 5151 c, and 5151 d and couple to thetop end 5155 of each of the compliant beams 5154 a, 5154 b, 5154 c, and5154 d for securing the compliant beams 5154 a, 5154 b, 5154 c, and 5154d within the RCC assembly 5150.

In some embodiments, the second plate 5152 includes a first via 5152 a,a second via 5152 b, a third via 5152 c, and a fourth via 5152 d, andeach the first via 5152 a, the second via 5152 b, the third via 5152 c,and the fourth via 5152 d creates an opening through the body of thesecond plate 5152. In some embodiments, the bottom end 5156 of each ofthe compliant beams 5154 a, 5154 b, 5154 c, and 5154 d is coupled to thesecond plate 5152 via the first via 5152 a, the second via 5152 b, thethird via 5152 c, and the fourth via 5152 d, respectively. In someembodiments, corresponding connectors (e.g., screws) are positionedthrough the vias 5152 a, 5152 b, 5152 c, and 5152 d and couple to thebottom end 5156 of each of the compliant beams 5154 a, 5154 b, 5154 c,and 5154 d for securing the compliant beams 5154 a, 5154 b, 5154 c, and5154 d within the RCC assembly 5150.

In some embodiments, the holes 5151 a, 5151 b, 5151 c, and 5151 d of thefirst plate 5151 are positioned along a first circumference of the firstplate 5151 and the vias 5152 a, 5152 b, 5152 c, and 5152 d of the secondplate 5152 are positioned along a second circumference of the secondplate 5152, and the first circumference has a smaller diameter than thatof the second circumference. In other words, in some embodiments, theholes 5151 a, 5151 b, 5151 c, and 5151 d are positioned closer to thecenter point of the first plate 5151 than the vias 5152 a, 5152 b, 5152c, and 5152 d are positioned with respect to the center point of thesecond plate 5152. In other words, each of the holes 5151 a, 5151 b,5151 c, and 5151 d has a smaller radial distance from the center pointof the first plate 5151 than that of each of the vias 5152 a, 5152 b,5152 c, and 5152 d from the center point of the second plate 5152.

Accordingly, in some embodiments, due to the difference in radialdistances between the holes 5151 a, 5151 b, 5151 c, and 5151 d and thevias 5152 a, 5152 b, 5152 c, and 5152 d, the compliant beams 5154 a,5154 b, 5154 c, and 5154 d are angled or tilted inwards towards thecenter point of the first plate 5151. In some embodiments, the degree ofthe angle or tilt is dependent on the difference in radial distancesbetween the holes 5151 a, 5151 b, 5151 c, and 5151 d and the vias 5152a, 5152 b, 5152 c, and 5152 d. For example, the greater the differencein the radial distances between the holes 5151 a, 5151 b, 5151 c, and5151 d and the vias 5152 a, 5152 b, 5152 c, and 5152 d, the greater thedegree of tilt is of the compliant beams 5154 a, 5154 b, 5154 c, and5154 d.

In some embodiments, the compliant beams 5154 a, 5154 b, 5154 c, and5154 d are adjusted or manufactured for particular parametercharacteristics, such as, but not limited to, shore hardness (hardnessof the material), tensile strength (point at which the materialtransitions from elastic to plastic deformation), elongation (change inlength over initial length at the tensile strength), modulus ofelasticity (slope of the curve in the elastic section of a stress/straincurve), length, and diameter. In one example, the compliant beams 5154a, 5154 b, 5154 c, and 5154 d have a shore hardness of about 60 A, atensile strength of about 4100 psi, an elongation of 500%, a modulus ofelasticity of 820 psi, a length of 1 in, and diameter 0.25 in. In someembodiments, the compliant beams 5154 a, 5154 b, 5154 c, and 5154 d havea shore hardness in a range from about 60 A to about 80 A, a tensilestrength in a range from about 4100 psi to about 4600 psi, an elongationin a range from about 450% to about 500%, and a modulus of elasticity ina range from about 820 psi to about 1020 psi.

According to various embodiments, the RCC assembly 5150 of the RCC probedevice 5100 is configured to adjust a center of compliance of the RCCprobe device 5100 (e.g., by adjusting the shape, angle of tilt,thickness, length, etc. of the compliant beams 5154 a, 5154 b, 5154 c,and 5154 d). In particular embodiments, the connection of the RCCassembly 5150 to the probe 5102 is configured to adjust the center ofcompliance to be at the tip of the probe 5102, on the scanning surface,or beneath the scanning surface such that the scanning surfaceinterposes the probe 5102 and the center of compliance.

In some embodiments, the center of compliance is adjusted from being atthe second end 5102 b of the probe 5102 (without the RCC assembly 5150)to being at the first end 5102 a of the probe 5102 or beyond (with theRCC assembly 5150 connected to the probe 5102). In some embodiments, theprecise location of the remote center of compliance is determined by thedesign of the RCC assembly 5150, such as, but not limited to, the numberand material of the compliant beams, the angle of tilt of the compliantbeams, the locations of the compliant beams, the length of the compliantbeams, thickness of the compliant beams, and so on.

FIG. 49 illustrates a top view of the first plate 5151 of the RCC probedevice 5100 according to various embodiments. FIG. 50 illustrates a topview of the second plate 5152 of the RCC probe device 5100 according tovarious embodiments.

Referring to FIGS. 54A-56B, in some embodiments, the first plate 5151has an origin or center point 5300 and the second plate 5152 has anorigin or center point 5350. In some embodiments, the center points 5300and 5350 are aligned such that a single axis passes through both thecenter point 5300 of the first plate 5151 and the center point 5350 ofthe second plate 5152.

In some embodiments, each of the holes 5151 a, 5151 b, 5151 c, and 5151d surround the center point 5300 of the first plate 5300, and each ofthe holes 5151 a, 5151 b, 5151 c, and 5151 d are spaced from adjacentholes at equal distances. In other words, the holes 5151 a, 5151 b, 5151c, and 5151 d are spaced along a circumference of the first plate 5151at equal intervals. In some embodiments, each of the holes 5151 a, 5151b, 5151 c, and 5151 d are a same first radial distance or first radiusr1 from the center point 5300.

In some embodiments, each of the vias 5152 a, 5152 b, 5152 c, and 5152 dsurround the center point 5350 of the second plate 5152, and each of thevias 5152 a, 5152 b, 5152 c, and 5152 d are spaced from adjacent vias atequal distances. In other words, the vias 5152 a, 5152 b, 5152 c, and5152 d are spaced along a circumference of the second plate 5152 atequal intervals. In some embodiments, each of the vias 5152 a, 5152 b,5152 c, and 5152 d are a same second radial distance or second radius r2from the center point 5350.

In some embodiments, the first radial distance r1 is less than thesecond radial distance r2, such that the compliant beams 5154 a, 5154 b,5154 c, and 5154 d are tilted inwards towards the center points 5300 and5350 when coupled to the first plate 5151 (via the holes 5151 a, 5151 b,5151 c, and 5151 d) and to the second plate 5152 (via the vias 5152 a,5152 b, 5152 c, and 5152 d). The degree or angle of tilt of thecompliant beams 5154 a, 5154 b, 5154 c, and 5154 d is dependent on thedifference between the first radial distance r1 and the second radialdistance r2. In other embodiments, the first radial distance r1 is equalto the second radial distance r2, or the first radial distance r1 isgreater than the second radial distance r2.

In some embodiments, the first radial distance r1 is less than thesecond radial distance r2 such that the angle of tilt of each of thecompliant beams 5154 a, 5154 b, 5154 c, and 5154 d is about 12.5 degreesinwards toward the center points 5300 and 5350, with respect to alateral upper surface of the second plate from which the compliant beams5154 a, 5154 b, 5154 c, and 5154 d extend towards the first plate 5151.In some embodiments, the distance from a center axis to centers of thecompliant beams 5154 a, 5154 b, 5154 c, and 5154 d (e.g., the distancebetween an axis that passes through the center points 5300 and 5350 anda midpoint of a compliant beam along the length of the compliant beam)is about 0.9 inches. In some embodiments, a projection ratio (ratio oflengths) of the compliant beams 5154 a, 5154 b, 5154 c, and 5154 d isabout 1.516.

FIG. 51 illustrates a free body diagram including the RCC probe device5100 according to various embodiments. Referring to FIGS. 54A-57, thediagram illustrates the function of the RCC probe device 5100. The freebody diagram illustrates the RCC probe device 5100 traveling laterallyalong a tilted scanning surface 5400 (e.g., skin or a head of a person).The RCC probe device 5100 travels laterally from left to right, orlaterally along the decline of the scanning surface 5400.

In some embodiments, the RCC assembly 5150 provides the remote center ofcompliance E about which the probe 5102 may rotate, and the remotecenter of compliance E may be located beneath the scanning surface 5400.As such, in some embodiments, due to the remote center of compliance Ebeing positioned beyond the probe 5102, the probe, no matter whereplaced, can align normal to the scanning surface 5400 (e.g., such thatsubstantially all of the concave surface 5103 of the probe 5102 contactsthe scanning surface 5400). In various embodiments, a force about theremote center of compliance E twists the probe 5102 into alignment withthe scanning surface 5400.

In some embodiments, in providing the remote center of compliance E, oneor more of the compliant beams 5154 a, 5154 b, 5154 c, and 5154 d of theRCC assembly 5150 will twist and/or bend to allow the probe 5102 toalign such that the probe 5102 rotates into the scanning surface 5400.As such, in some embodiments, when a linear misalignment occurs, acontact force translates the probe away, and when an angularmisalignment occurs, a contact moment turns the probe 5102 about theremote center of compliance E, allowing for the probe 5102 to alignnormal with the scanning surface 5400. Accordingly, in variousembodiments, the probe 5102, with the aid of the attached RCC assembly5150, will auto-align normal to the scanning surface 5400 along whichthe probe 5102 is sliding.

In some embodiments, the behavior of the RCC probe device 5100 shown inFIG. 51 can be represented by the following equations. In the followingequations for a particular rod or beam,

L is the longitudinal length

E is the modulus of elasticity

A is the cross-sectional area

A_(sx) is the shear area in the x direction

A_(sy) is the shear area in the y direction

I_(x) is the area moment of inertia in the x direction

I_(y) is the area moment of inertia in the y direction

v is Poisson's ratio

G is the shear modulus, which is equal to E/2(1+v)

J is the polar moment of inertia

O is the origin point of a beam in the longitudinal length direction

R is the distance from a center axis to a midpoint of a compliant beam

$\begin{matrix}{\lambda_{zy} = {\lambda_{z} = {\lambda_{y} = \frac{12{EI}}{L^{3}\left( {1 + \Phi} \right)}}}} & (1) \\{\lambda_{z} = \frac{AE}{L}} & (2) \\{µ_{zy} = {µ_{z} = {µ_{y} = \frac{EI}{L}}}} & (3) \\{µ_{z} = \frac{GJ}{L}} & (4) \\{p = {\frac{EO}{R} = \begin{matrix}{{\lambda_{z}\cos^{2}\theta} + \lambda_{y + {\lambda_{z}\sin^{2}\theta}}} \\{\left( {\lambda_{z} - \lambda_{x}} \right)\cos \; {\theta sin\theta}}\end{matrix}}} & (5) \\{\Phi_{z} = \frac{12{EI}_{y}}{{GA}_{xz}L^{2}}} & (6) \\{\Phi_{y} = \frac{12{EI}_{z}}{{GA}_{xy}L^{2}}} & (7)\end{matrix}$

The above used terms, including “attached,” “connected,” “secured,” andthe like are used interchangeably. In addition, while certainembodiments have been described to include a first element as being“coupled” (or “attached,” “connected,” “fastened,” etc.) to a secondelement, the first element may be directly coupled to the second elementor may be indirectly coupled to the second element via a third element.

The algorithmic subject matter and the operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. The algorithmic subject matterdescribed in this specification can be implemented as one or morecomputer programs, e.g., one or more circuits of computer programinstructions, encoded on one or more computer storage media forexecution by, or to control the operation of, data processingapparatuses. Alternatively or in addition, the program instructions canbe encoded on an artificially generated propagated signal, e.g., amachine-generated electrical, optical, or electromagnetic signal that isgenerated to encode information for transmission to suitable receiverapparatus for execution by a data processing apparatus. A computerstorage medium can be, or be included in, a computer-readable storagedevice, a computer-readable storage substrate, a random or serial accessmemory array or device, or a combination of one or more of them. While acomputer storage medium is not a propagated signal, a computer storagemedium can be a source or destination of computer program instructionsencoded in an artificially generated propagated signal. The computerstorage medium can also be, or be included in, one or more separatecomponents or media (e.g., multiple CDs, disks, or other storagedevices). The algorithmic operations described in this specification canbe implemented as operations performed by a data processing apparatus ondata stored on one or more computer-readable storage devices or receivedfrom other sources.

The terms “data processing system” “computing device” “component” or“data processing apparatus” encompass various apparatuses, devices, andmachines for processing data, including by way of example a programmableprocessor, a computer, a system on a chip, or multiple ones, orcombinations of the foregoing. The apparatus can include special purposelogic circuitry, e.g., an FPGA (field programmable gate array) or anASIC (application specific integrated circuit). The apparatus can alsoinclude, in addition to hardware, code that creates an executionenvironment for the computer program in question, e.g., code thatconstitutes processor firmware, a protocol stack, a database managementsystem, an operating system, a cross-platform runtime environment, avirtual machine, or a combination of one or more of them. The apparatusand execution environment can realize various different computing modelinfrastructures, such as web services, distributed computing and gridcomputing infrastructures.

A computer program (also known as a program, software, softwareapplication, app, script, or code) can be written in any form ofprogramming language, including compiled or interpreted languages,declarative or procedural languages, and can be deployed in any form,including as a stand-alone program or as a module, component,subroutine, object, or other unit suitable for use in a computingenvironment. A computer program can correspond to a file in a filesystem. A computer program can be stored in a portion of a file thatholds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The algorithmic processes and logic flows described in thisspecification can be performed by one or more programmable processorsexecuting one or more computer programs (e.g., components or modules ofthe system 1040 or system 1080) to perform actions by operating on inputdata and generating output. The processes and logic flows can also beperformed by, and apparatuses can also be implemented as, specialpurpose logic circuitry, e.g., an FPGA (field programmable gate array)or an ASIC (application specific integrated circuit). Devices suitablefor storing computer program instructions and data include all forms ofnon-volatile memory, media and memory devices, including by way ofexample semiconductor memory devices, e.g., EPROM, EEPROM, and flashmemory devices; magnetic disks, e.g., internal hard disks or removabledisks; magneto optical disks; and CD ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,special purpose logic circuitry.

The subject matter described herein can be implemented in a computingsystem that includes a back end component, e.g., as a data server, orthat includes a middleware component, e.g., an application server, orthat includes a front end component, e.g., a client computer having agraphical user interface or a web browser through which a user caninteract with an implementation of the subject matter described in thisspecification, or a combination of one or more such back end,middleware, or front end components. The components of the system can beinterconnected by any form or medium of digital data communication,e.g., a communication network. Examples of communication networksinclude a local area network (“LAN”) and a wide area network (“WAN”), aninter-network (e.g., the Internet), and peer-to-peer networks (e.g., adhoc peer-to-peer networks).

The computing system such as system 1040 or system 1080 can includeclients and servers. A client and server are generally remote from eachother and typically interact through a communication network. Therelationship of client and server arises by virtue of computer programsrunning on the respective computers and having a client-serverrelationship to each other. In some implementations, a server transmitsdata (e.g., data packets representing a content item) to a clientcomputing device (e.g., for purposes of displaying data to and receivinguser input from a user interacting with the client computing device).Data generated at the client computing device (e.g., a result of theuser interaction) can be received from the client computing device atthe server.

While operations are depicted in the drawings in a particular order,such operations are not required to be performed in the particular ordershown or in sequential order, and all illustrated operations are notrequired to be performed. Actions described herein can be performed in adifferent order.

The separation of various system components does not require separationin all implementations, and the described program components can beincluded in a single hardware or software product.

Having now described some illustrative implementations, it is apparentthat the foregoing is illustrative and not limiting, having beenpresented by way of example. In particular, although many of theexamples presented herein involve specific combinations of method actsor system elements, those acts and those elements may be combined inother ways to accomplish the same objectives. Acts, elements andfeatures discussed in connection with one implementation are notintended to be excluded from a similar role in other implementations orimplementations.

The phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including” “comprising” “having” “containing” “involving”“characterized by” “characterized in that” and variations thereofherein, is meant to encompass the items listed thereafter, equivalentsthereof, and additional items, as well as alternate implementationsconsisting of the items listed thereafter exclusively. In oneimplementation, the systems and methods described herein consist of one,each combination of more than one, or all of the described elements,acts, or components.

Any references to implementations or elements or acts of the systems andmethods herein referred to in the singular may also embraceimplementations including a plurality of these elements, and anyreferences in plural to any implementation or element or act herein mayalso embrace implementations including only a single element. Referencesin the singular or plural form are not intended to limit the presentlydisclosed systems or methods, their components, acts, or elements tosingle or plural configurations. References to any act or element beingbased on any information, act or element may include implementationswhere the act or element is based at least in part on any information,act, or element.

Any implementation disclosed herein may be combined with any otherimplementation or embodiment, and references to “an embodiment,” “someembodiments,” “various embodiments,” “one embodiment,” or the like arenot necessarily mutually exclusive and are intended to indicate that aparticular feature, structure, or characteristic described in connectionwith the embodiment may be included in at least one implementation orembodiment. Such terms as used herein are not necessarily all referringto the same embodiment. Any embodiment may be combined with any otherembodiment, inclusively or exclusively, in any manner consistent withthe aspects and embodiments disclosed herein.

References to “or” may be construed as inclusive so that any termsdescribed using “or” may indicate any of a single, more than one, andall of the described terms. For example, a reference to “at least one of‘A’ and ‘β’” can include only ‘A’, only ‘B’, as well as both ‘A’ and‘B’. Such references used in conjunction with “comprising” or other openterminology can include additional items.

Where technical features in the drawings, detailed description or anyclaim are followed by reference signs, the reference signs have beenincluded to increase the intelligibility of the drawings, detaileddescription, and claims. Accordingly, neither the reference signs northeir absence have any limiting effect on the scope of any claimelements.

The systems and methods described herein may be embodied in otherspecific forms without departing from the characteristics thereof. Forexample, components of the data processing system 105 need not beseparate components, and one component can include other components.Processors of one or more computing devices (e.g., servers) can includeor execute components of the data processing system 105. The foregoingimplementations are illustrative rather than limiting of the describedsystems and methods. Scope of the systems and methods described hereinis thus indicated by the appended claims, rather than the foregoingdescription, and changes that come within the meaning and range ofequivalency of the claims are embraced therein.

What is claimed is:
 1. A tool for acquiring and optimizing a signal froma subject by a robotic device, comprising: a transducer configured totransmit acoustic energy; a database including one or more seed points,each of the seed points corresponding to a different coordinate locationon the subject; and a processing circuit configured to: move thetransducer to a first seed point of the seed points; and scan at oraround the first seed point by following a first predefined search pathalong the subject.
 2. The tool of claim 1, wherein the processingcircuit is further configured to: store a first point of interest at oralong the first predefined search path; and in response to storing thefirst point of interest, move the transducer to the first point ofinterest and scan at or around the first point of interest by followinga second predefined search path.
 3. The tool of claim 2, wherein thefirst predefined search path is different from the second predefinedsearch path.
 4. The tool of claim 3, wherein the second predefinedsearch path defines finer movements of the transducer than the firstpredefined search path does.
 5. The tool of claim 2, wherein storing thefirst point of interest comprises: determining whether the first pointof interest is greater than a first energy threshold; and in response todetermining that the first point of interest is greater than the firstenergy threshold, storing the first point of interest.
 6. The tool ofclaim 5, wherein the processing circuit is further configured to: storean improved point of interest at or along the second predefined searchpath; and in response to storing the improved point of interest, movethe transducer to the improved point of interest and scan at or aroundthe improved point of interest by following a third predefined searchpath.
 7. The tool of claim 6, wherein the third predefined search pathdefines finer movements of the transducer than the second predefinedsearch path does, and the second predefined search path defines finermovements of the transducer than the first predefined search path does.8. The tool of claim 6, wherein storing the improved point of interestcomprises: determining whether the improved point of interest is greaterthan an increased energy threshold, the increased energy thresholdhigher than the first energy threshold; and in response to determiningthat the improved point of interest is greater than the increased energythreshold, also storing the improved point of interest.
 9. The tool ofclaim 2, wherein the processing circuit is further configured to: movethe transducer to a second seed point of the seed points, the secondseed point corresponding to the different coordinate location on thesubject than the first seed point; and scan at or around the second seedpoint by following the first predefined search path along the subject.10. The tool of claim 2, wherein the processing circuit is furtherconfigured to store a second point of interest at or along the firstpredefined search path, the second point of interest corresponding tothe different coordinate location on the subject than the first point ofinterest.
 11. The tool of claim 10, wherein the processing circuit isfurther configured to rank the first point of interest and the secondpoint of interest based on their individual energy levels.
 12. The toolof claim 11, wherein the processing circuit is further configured to:select a coordinate location along the subject based on a higher-rankingpoint of interest corresponding to either the stored first point ofinterest or the stored second point of interest; move the transducer tothe higher-ranking point of interest; and monitor the subject via thetransducer at the higher-ranking point of interest.
 13. The tool ofclaim 12, wherein the processing circuit is further configured to:determine whether a monitoring energy level at the higher-ranking pointof interest degrades below a stored energy level corresponding to thehigher-ranking point of interest by a predetermined percentage; and inresponse to the higher-ranking point of interest degrading below thestored energy level by the predetermined percentage, adjust a positionof the transducer at the higher-ranking point of interest.
 14. The toolof claim 2, wherein storing the first point of interest comprises:detecting the first point of interest based on one or more morphologicalfeatures of an ultrasound waveform captured by the transducer; and inresponse to detecting the first point of interest, storing the firstpoint of interest.
 15. The tool of claim 1, wherein each of the one ormore seed points corresponds to a coordinate location that has arelatively high probability of detection of a relatively high energylevel as determined across a plurality of prior scanned subjects. 16.The tool of claim 15, wherein the one or more seed points are sorted byat least one of race, gender, or age of the plurality of subjects. 17.The tool of claim 1, wherein the transducer is configured to transmitultrasound energy and the robotic device includes a Transcranial Doppler(TCD) device.
 18. The tool of claim 1, wherein each of the one or moreseed points corresponds to a coordinate location along an ultrasoundacoustic window of the subject.
 19. The tool of claim 1, wherein thefirst predefined search path includes a spiral search path having acenter point corresponding to the first seed point.
 20. The tool ofclaim 1, which stores coordinate points of interest that have energythresholds above a predetermined value found during a predefined searchpath which can later move a robotic transducer back to one or more ofthe stored points of interest.
 21. The tool of claim 1, wherein thetransducer is configured to move along an x-axis, a y-axis perpendicularto the x-axis, and a z-axis perpendicular to the x-axis and the y-axis,along the first predefined search path.
 22. The tool of claim 1, whereinthe transducer is configured to pan and tilt along the first predefinedsearch path.
 23. The tool of claim 1, wherein the processing circuit isfurther configured to: store a first point of interest at or along thefirst predefined search path; and in response to storing the first pointof interest, perform a hill climb search using the transducer at andaround the first point of interest.
 24. A method for acquiring andoptimizing a signal from a subject by a robotic device, the methodcomprising: moving, by the robotic device, a transducer configured totransmit acoustic energy to a first seed point of one or more seedpoints, each of the one or more seed points corresponding to a differentcoordinate location at the subject; and scanning, by the robotic device,at and around the first seed point by following a first predefinedsearch path along the subject.
 25. A non-transitory processor-readablemedium storing processor-readable instructions such that, when executed,causes a processor to acquire and optimize a signal from a subject by arobotic device by: moving, by the robotic device, a transducerconfigured to transmit acoustic energy to a first seed point of one ormore seed points, each of the one or more seed points corresponding to adifferent coordinate location at the subject; and scanning, by therobotic device, at and around the first seed point by following a firstpredefined search path along the subject.